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' I 



Secretary of the 
Smithsonian Institution 


XS. - 

Published by 






Robert Evans Snodgrass 

United States Bureau of Entomology 






Copyright 1930, by 

[Printed in the United States of America] 
All rights reserved 

Copyright Under the Articles of the Copyright Convention 

of the Pan-American Republics and the 

United States, August II, 1910 


Preface i 

I. The Grasshopper i 

II. The Grasshopper's Cousins .... 26 

III. Roaches and Other Ancient Insects . 77 

IV. Ways and Means of Living .... 99 
V. Termites 1 25 

VI. Plant Lice 152 

VII. The Periodical Cicada 182 

VIII. Insect Metamorphosis 226 

IX. The Caterpillar and the Moth . . 262 

X. Mosquitoes and Flies 314 

Index 355 
























The Carolina Locust Frontispiece 

Miscellaneous insects 28 

The Green Apple Aphis 154 

The Rosy Apple Aphis 160 

The Apple-grain Aphis 170 

Nymph of the Periodical Cicada 184 

Newly emerged Cicada 192 

Cicada laying eggs 198 

Egg nests and eggs of the Periodical Cicada . . 212 

Two species of large moths 228 

The Cecropia Moth and the Polyphemus Moth 230 

The Ribbed-cocoon Maker 252 

The Peach-borer Moth 254 

The Red-humped Caterpillar 260 

The Tent Caterpillar 262 


Young grasshoppers 2 

End structures of a grasshopper's body 3 

Grasshopper laying eggs 4 

Egg-pods of a grasshopper 5 

Eggs of a grasshopper . . 6 

Young grasshopper emerging from the egg 8 

Eggs of a katydid 10 

A young grasshopper 12 

The growth stages of a grasshopper 13 

A parasitic fly 20 

Blister beetles 22 

A triungulin larva of a blister beetle 23 

Second-stage larva of a blister beetle 24 

Examples of Arthropoda 27 

A "singing" grasshopper 29 

Another "singing" grasshopper 31 

The feet of Orthoptera 33 

Sound-making organs of a meadow grasshopper ... 34 

19. Sound-making organs and ears of a conehead katydid 35 

20. Auditory organ of a katydid 37 

2i. A bush katydid 38 

22. The oblong-winged katydid 40 

23. The angular-winged katydid 42 

24. The true katydid 44 

25. The katydid in various attitudes 45 

26. Sound-making organs of the katydid 48 

27. A conehead katydid 50 

28. The robust katydid 51 

29. The common meadow katydid 52 

30. The handsome meadow katydid 53 

31. The slender meadow katydid 53 

32. The Coulee cricket 55 

23. Wings of a tree cricket 56 

34. A mole cricket 57 

35. The striped ground cricket 59 

36. The common black cricket 61 

37. The snowy tree cricket 64 

38. Antennal marks of the tree crickets 66 

39. The narrow-winged tree cricket 67 

40. A broad-winged tree cricket 68 

41. Back glands of a tree cricket 68 

42. The jumping bush cricket 70 

43. The common walking-stick insect 71 

44. A gigantic walking-stick insect 72 

45. A leaf insect 73 

46. The praying mantis 74 

47. A shield-bearing mantis 75 

48. Egg case of a mantis 75 

49. Common household roaches 78 

50. Egg cases of roaches 79 

51. Young of the Croton bug 81 

52. The house centipede 83 

53. Wings of a cockroach 84 

54. A Paleozoic forest 86 

55. Fossil roaches 90 

56. Early fossil insects 91 

57. Machilis 93 

58. Dragonflies 94 

59. A young dragonfly 96 

60. A mayfly 97 

61. A young mayfly 98 

62. The relation of the germ cells and body cells .... 100 

63. External structure of an insect 102 

64. Leg of a young grasshopper 103 

65. Legs of a honeybee 10^ 

66. Head and mouth parts of a grasshopper 106 

67. Internal organs of a grasshopper 108 

68. Alimentary canal of a grasshopper 109 

69. Heart of an insect 112 

70. Respiratory system of a caterpillar 115 

71. The brain of a grasshopper 118 

72. Nervous system of a grasshopper 120 

73. Reproductive organs of an insect 122 

74. Ovipositor of a katydid 123 

75. Termites 126 

76. Termite work in a piece of wood 128 

77. Worker and soldier castes and young of a termite . . 130 

78. Heads of termite soldiers 132 

79. Winged caste of a termite 133 

80. Short-winged reproductive caste of a termite .... 135 

81. A wingless termite queen 138 

82. Termite king and queen 141 

83. Wing of an ordinary termite 145 

84. Wings of a Mastotermes 146 

85. Section of an underground termite nest 147 

86. Four types of termite nests 149 

87. Large termite nest 150 

88. Group of aphids feeding 153 

89. How an aphis feeds 154 

90. Section of the beak of an aphis 156 

91. Aphis eggs 157 

92. Aphis eggs just before hatching 158 

93. Young aphis emerging from the egg 159 

94. Young aphids on apple buds 161 

95. Young of three species of apple aphids 162 

96. Apple leaves infested by green apple aphis 163 

97. The green apple aphis 165 

98. The rosy apple aphis on apple 168 

99. The rosy apple aphis on plantain 169 

100. Male and female of the rosy apple aphis 170 

101. Some common aphids of the garden 171 

102. A ladybird beetle 173 

103. The aphis-lion 174 

104. The golden-eye, Chrysopa 176 

105. Larva of a syrphus fly feeding on aphids 176 

106. Adult syrphus flies . 177 

107. A parasitized aphis 178 

108. An aphis parasite, Aphidius 178 

109. A female Aphidius inserting an egg in a living aphis . 178 

no. Parasitized aphids on parasite cocoons 179 

ill. A parasitized lady-beetle larva 181 

112. A common cicada 183 

[13- Young nymph of the periodical cicada 



Older nymph of the periodical cicada l8 7 

15. Underground cells of the periodical cicada l88 

16. Fore leg of a cicada nymph 9 

17. Cicada turrets r 9 2 

18. Transformation of the cicada '9" 

19. Two forms of the periodical cicada 2 °° 

20. Male of the periodical cicada 2 °° 

21. The head and beak of a cicada 2 ° 2 

22. The sucking organ of a cicada 2o 4 

23. Section of a cicada's body 2 °" 

24. Sound-making organs of a cicada 2 °9 

25. Egg and newly-hatched nymph of the cicada .... 220 

26. Young cicada nymph 22 4 

27. Moths of the fall webworm 22 7 

28. The celery caterpillar and butterfly 22 9 

29. The Luna moth 2 3° 

30. Life of a cutworm 2 3 J 

31. A maybeetle and its grub ' 2 33 

32. Life stages of a lady-beetle 2 35 

23- Life stages of a wasp 2 3^ 

34. A dragonfly nymph 2 3 8 

35. Various habitats of plant-feeding caterpillars .... 241 

36. External structure of a caterpillar 242 

37. Adult and larval forms of beetles 244 

38. Diagram of insect metamorphosis 246 

39. Springtails 247 

40. A bristletail, Thermobia 248 

41. The relation of a pupa to other insect forms .... 254 

42. Muscle attachment on the body wall 256 

43. Young tent caterpillars 263 

44. Eggs and newly-hatched tent caterpillars 265 

45. First tent of young tent caterpillars 267 

46. Young tent caterpillars on a sheet of silk 268 

47. Mature tent caterpillars feeding 271 

48. Mature tent caterpillars 273 

49. Twigs denuded by tent caterpillars 278 

50. A tent caterpillar jumping from a tree 280 

51. Cocoon of a tent caterpillar 282 

52. Head of a tent caterpillar 284 

53. Jaws of a tent caterpillar 284 

54. Internal organs of a caterpillar 285 

55. The spinning organs of a caterpillar 287 

56. The alimentary canal of a tent caterpillar 288 

57. Crystals formed in the Malpighian tubules 289 

58. The fat-body of a caterpillar 291 

59. Transformation of the tent caterpillar 294 

160. Contents of the pupal blood 303 

161. Moths of the tent caterpillar 307 

162. Head of a tent caterpillar moth 308 

163. Head of a peach borer moth 308 

164. Transformation of the alimentary canal 310 

165. Reproductive organs of a female moth 312 

166. Young tent caterpillars in the egg 313 

167. A robber fly . 316 

168. Wings of insects 317 

169. The black horsefly 320 

170. Mouth parts of a horsefly 322 

171. Structure of a fly maggot 325 

172. Rat-tailed maggots 326 

173. Larva and pupa of a horsefly 328 

174. Life stages of a mosquito 330 

175. Structure of a mosquito larva 332 

176. Mouth parts of a mosquito 334 

177. A male mosquito 335 

178. Mosquito larvae 337 

179. Mosquito pupae 339 

180. The female malaria mosquito 340 

181. Feeding positions of mosquito laivae 341 

1 82. Life stages of the house fly 344 

183. Head and mouth parts of the house fly 346 

184. Head of the stable fly 347 

185. A tsetse fly 349 

186. Head and mouth parts of the tsetse fly 351 





In the early days of zoology there were naturalists who 
spent much time out of doors observing the ways of the 
birds, the insects, and the other creatures of the fields and 
woods. These men were not steeped in technical learning. 
Nature was a source of inspiration and a delight to them; 
her manifestations were to be taken for granted and not 
questioned too closely. A mind able to accept appear- 
ances for truth can express itself in the words of everyday 
language — for language was invented long ago when 
people did not bother themselves much with facts — and 
some of those early writers, inspired direct from nature, 
have left us a delightful literature based on their observa- 
tions and reflections on the things of nature. The public 
has liked to read the works of these men because they tell 
of interesting things in an interesting way and in words 
that can be understood. 

At the same time there was another class of nature 
students who did not care particularly what an animal did, 
but who wanted to know how it was made. The devotees 
of this cult looked at things through microscopes; they 
dissected all kinds of creatures in order to learn their con- 
struction and their structural relationships. But they 
found many things on the inside of animals that had never 
been named, so for these things they invented names; and 
when their books were printed the public could not read 
them because of the strange words they contained. More- 
over, since nature does not usually embellish her hidden 
works, the anatomists could not enhance their writings 
with descriptive metaphors in the way the outdoor 
naturalists could. Consequently, the students of struc- 
ture have never come into favor with the reading public, 
and their works are denounced as dry and tedious. 



Then there arose still another group of inquiring minds. 
Members of this school could not see anything worth while 
in knowing merely either what an animal did or how it was 
made. They devoted their efforts to discovering the 
secrets of its workings. They invented instruments for 
measuring the power of its muscles, for testing the nature 
of the force that resides in its nerves; they made analyses 
of its food and its tissues; they devised all kinds of experi- 
ments for revealing the causes of its behavior. The work- 
ers in this branch, the physiologists, had to have a con- 
siderable grounding in physics and chemistry; conse- 
quently they came to write more or less in the languages 
of those sciences and to express themselves in chemical and 
mathematical formulae. Their writings are hard for the 
public to understand. Their statements, moreover, are 
often at odds with preconceived "ideas, since precon- 
ceived ideas are conceived in ignorance, and the public at 
large does not take to this sort of thing — it cherishes above 
all its inherited opinions. 

Therefore the old-time naturalist is still venerated, as 
he deserves to be, and those who call themselves "nature 
lovers" still like to decry the laboratory worker as an evil 
being who would take the beauty from nature and destroy 
the soul of man. A modern writer of the old school may 
sell his wares, but when something goes wrong with his 
stomach or his nerves, or when his plants or his animals 
are attacked by disease, it is the knowledge of the labora- 
tory scientist that comes to his aid. 

The reason that the specific truths of nature must be 
found out in laboratories is that there are too many things 
mixed together in the fields. The laboratory naturalist 
endeavors to untangle the confusion of elements in the 
outdoor environment and to isolate the different factors 
that affect the life and behavior of an animal, in order 
that he may be sure with just what he is dealing in his ef- 
forts to determine the value of each one separately. By 
creating a set of artificial environments in each of which 


only one natural factor is allowed to be operative at the 
same time, he is in a position to observe correctly, after 
repeated experiments, just what effects proceed from this 
cause and what from that. 

Nature study, in the superficial sense, may be enter- 
taining. We of the present age, however, must learn to 
take a deeper insight into the lives of the other living 
things about us. Insects, for example, are not curiosities; 
they are creatures in common with ourselves bound by 
the laws of the physical universe, which laws decree that 
everything alive must live by observing the same ele- 
mental principles that make life possible. It is only in 
the ways and means by which we comply with the condi- 
tions laid down by physical nature that we differ. 

Many sincere people find it difficult to believe in evolu- 
tion. Their difficulty arises largely from the fact that 
they look to the differences in structure between the 
diverse types of living things and do not see the unity in 
function that underlies all physical forms of life. Conse- 
quently they do not understand that evolution means the 
progressive structural divergence of the various life forms 
from one another, resulting from the different ways that 
each has adopted and perfected for accomplishing the 
same ends. Man and the insects represent the extremi- 
ties of two most divergent lines of animal evolution, and 
by reason of the very disparity in structure between us the 
bond of unity in function becomes all the more apparent. 
A study of insects, therefore, will help us the better to 
understand ourselves in so far as it helps us to grasp the 
fundamental principles of life. 

Some writers seem to think that the sole purpose of 
writing is that it shall be read. Just as reasonable would 
it be to claim that the only purpose of food is that 
it shall be eaten. In the following chapters the reader 
is offered an entomological menu in which the consider- 
ation of nutrient value and the requirements of a balanced 
meal have been given first attention. As a concession to 



palatability, however, as much as possible of the dis- 
tasteful matter of technical terminology has been ex- 
tracted, and an attempt has been made to avoid the pure 
scientific style of literary cuisine, which forbids the use of 
all those ingredients whose object is that of inflation but 
which, if properly admixed, will greatly aid in the process 
of digestion. 

Much of the material in several chapters is taken from 
articles already printed in the Annual Reports of the 
Smithsonian Institution. The original drawings of most 
of the color plates and line cuts are the property of the 
United States Bureau of Entomology, though some of 
them are here published for the first time. 

R. E. S. 





Sometime in spring, earlier or later according to the lati- 
tude or the season, the fields, the lawns, the gardens, sud- 
denly are teeming with young grasshoppers. Comical little 
fellows are they, with big heads, no wings, and strong hind 
legs (Fig. i). They feed on the fresh herbage and hop 
lightly here and there, as if their existence in no way in- 
volved the mystery of life nor raised any questions as to 
why they are here, how they came to be here, and whence 
they came. Of these questions, the last is the only one 
to which at present we can give a definite answer. 

If we should search the ground closely at this season, 
it might be possible to see that the infant and apparently 
motherless grasshoppers are delivered into the visible 
world from the earth itself. With this information, a 
nature student of ancient times would have been satisfied 
—grasshoppers, he would then announce, are bred spon- 
taneously from matter in the earth; the public would 
believe him, and thereafter would countenance no con- 
trary opinion. There came a time in history, however, 
when some naturalist succeeded in overthrowing this idea 
and established in its place the dictum that every life comes 
from an egg. This being still our creed, we must look for 
the grasshopper's egg. 



The entomologist who plans to investigate the lives ot 
grasshoppers finds it easier to begin his studies the year 
before; instead of sitting the earth to find the eggs from 
which the young insects are hatched in the spring, he ob- 
serves the mature insects in the fall and secures a supply ot 
eggs freshly laid by the females, either in the field or in 
cages properly equipped for them. In the laboratory then 

Fig. I. Young grasshoppers 

he can closely watch the hatching and observe with ac- 
curacy the details of the emergence. So, let us reverse the 
calendar and take note of what the mature grasshoppers of 
last season's crop are doing in August and September. 

First, however, it is necessary to know just what insect 
is a grasshopper, or what insect we designate by the name; 
for, unfortunately, names do not always signify the same 
thing in different countries, nor is the same name always 
applied to the same thing in different parts of the same 
country. It happens to be thus with the term "grass- 
hopper." In most other countries they call grasshoppers 
"locusts," or rather, the truth is that we in the United 
States call locusts "grasshoppers," for we must, of course, 
concede priority to Old World usage. When you read of 
a "plague of locusts," therefore, you must understand 
"grasshoppers." But a swarm of "seventeen-year locusts" 
means quite another insect, neither locust nor grasshopper 
— correctly, a cicada. All this mix-up of names and many 
other misfits in our popular natural history parlance we 



can blame probably on the early settlers of our States, who 
bestowed upon the creatures encountered in the New 
World the names of animals familiar at home; but, having 
no zoologists along for their guidance, they made many 
errors of identification. Scientists have sought to estab- 
lish a better state of nomenclatural affairs by creating a 
set of international names tor all living things, but since 
their names are in Latin, 
or Latinized Greek, thev 
are seldom practicable 
for everyday purposes. 

Knowing now that a 
grasshopper is a locust, 
it only needs to be 
said that a true locust 
is any grasshopperlike 
insect with short horns, 
or antennae (see Fron- 
tispiece). A similar in- 
sect with long slender 
antennae is either a 
katydid (Figs. 23, 24), 
or a member of the 
cricket family (Fig. 39). 
If you will collect and 
examine a tew specimens 
ot locusts, which we will 
proceed to call grass- 
hoppers, you may ob- 
serve that some have 
the rear end of the body smoothly rounded and that others 
have the body ending in four horny prongs. The second 
kind are females (Fig. 2 B); the others (A) are males and 
may be disregarded for the present. It is one of the pro- 
visions of nature that whatever any creature is compelled 
by its instinct to do, for the doing of that thing it is pro- 
vided with appropriate tools. Its tools, however, unless 


Rig. 2. The end of the body of a male and 

a female grasshopper 
The body, or abdomen, of a male (A) is 
bluntly rounded; that of the female (B) 
bears two pairs of thick prongs, which 
constitute the egg-laying organ, or ovi- 
positor (Uvp) 


it is a human animal, are always parts of its body, or of its 
jaws or its legs. The set of prongs at the end of the body 
of the female grasshopper constitutes a digging tool, an 
instrument by means of which the insect makes a hole in 
the ground wherein she deposits her eggs. Entomologists 
call the organ an ovipositor, or egg-placer. Figure 2 B 

Pre. 3. A female grasshopper in the position of depositing a pod of eggs in a 

hole in the ground dug with her ovipositor. (Drawn from a photograph in - 

U. S. Bur. Ent.) 

shows the general form of a grasshopper's ovipositor; the 
prongs are short and thick, the points of the upper pair are 
curved upward, those of the lower bent downward. 

When the female grasshopper is ready to deposit a 
batch of eggs, she selects a suitable spot, which is almost 
any place in an open sunny field where her ovipositor can 
penetrate the soil, and there she inserts the tip of her 
organ with the prongs tightly closed. When the latter 
are well within the ground, they are probably spread 
apart so as to compress the earth outward, for the drilling 



process brings no detritus to the surface, and gradually 
the end of the insect's body sinks deeper and deeper, until 
a considerable length of it is buried in the ground (Fig. 3). 
Now all is ready for the discharge of the eggs. The exit 
duct from the tubes of the ovary, which are filled with 
eggs already ripe, opens just below and between the bases 
of the lower prongs of the ovipositor, so that, when the 
upper and lower prongs are separated, the eggs escape 
from the passage between them. While the eggs are 
being placed in the bottom of the well, a frothy gluelike 
substance from the body of 
the insect is discharged 
over them. This sub- 
stance hardens about the 
eggs as it dries, but not in 
a solid mass, for its frothy 
nature leaves it full of 
cavities, like a sponge, and 
affords the eggs, and the 
young grasshoppers when 
they hatch, an abundance 
of space for air. To the 
outside of the covering 
substance, while it is fresh 
and sticky, particles of 
earth adhere and make a 
finely granular coating 
over the mass, which, when hardened, looks like a small 
pod or capsule that has been molded into the shape of the 
cavity containing it (Fig. 4). The number of eggs within 
each pod varies greatly, some pods containing only half 
a dozen eggs, and others as many as one hundred and 
fifty. Each female also deposits several batches of eggs, 
each lot in a separate burrow and pod, before her egg 
supply is exhausted. Some species arrange the eggs 
regularly in the pods, while others cram them in hap- 

Fig. 4. Egg pods of a grasshopper, show- 
ing various shapes; one opened exposing 
the eggs within. (Much enlarged) 



Fit;. J. Eggs of a grasshopper; one split at the upper 
end, showing the young grasshopper about to emerge 

The egg of a grasshopper is elongate-oval in shape 
'Fig. Oj those of ordinary-sized grasshoppers being about 
three-sixteenths of an inch in length, or a little longer. 

The ends of the 
eggs are rounded 
or bluntly 
pointed, and the 
lower extremity 
(the egg being 
generally placed 
on end) appears 
to have a small 
cap over it. One 
side of the egg is 
always more 
curved than the 
opposite side, 
which may be al- 
most straight. 
The surface is smooth and lustrous to the naked eye, but 
under the microscope it is seen to be marked off by slightly 
raised lines into many small polygonal areas. 

Within each egg is the germ that is to produce a new 
grasshopper. This germ, the living matter of the egg, is 
but a minute fraction of the entire egg contents, for the 
bulk of the latter consists of a nutrient substance, called 
yolk, the purpose of which is to nourish the embryo as it 
develops. The tiny germ contains in some form, that even 
the strongest microscope will not reveal, the properties 
which will determine every detail of structure in the future 
grasshopper, except such as may be caused by external cir- 
cumstances. It would be highly interesting to follow the 
course of the development of the embryo insect within the 
egg, and most of the important facts about it are known; 
but the story would be entirely too long to be given here, 
though a tew things about the grasshopper's development 
should be noted. 



The egg germ begins its development as soon as the eggs 
are laid in the fall. In temperate or northern latitudes, 
however, low temperatures soon intervene, and develop- 
ment is thereby checked until the return of warmth in the 
spring — or until some entomologist takes the eggs into an 
artificially heated laboratory. The eggs of some species of 
grasshoppers, if brought indoors before the advent of 
freezing weather and kept in a warm place, will proceed 
with their development, and young grasshoppers will 
emerge from them in about six weeks. On the other hand, 
the eggs of certain species, when thus treated, will not 
hatch at all; the embryos within them reach a certain 
stage of development and there they stop, and most of 
them never will resume their growth unless they are sub- 
jected to a freezing temperature! But, after a thorough 
chilling, the young grasshoppers will come out, even in 
January, if the eggs are then transferred to a warm place. 

To refuse to complete its development until frozen and 
then warmed seems like a preposterous bit of inconsistency 
on the part of an insect embryo; but the embryos of many 
kinds of insects besides the grasshopper have this same 
habit from which they will not depart, and so we must con- 
clude that it is not a whim but a useful physiological prop- 
erty with which they are endowed. The special deity of 
nature delegated to look after living creatures knows well 
that Boreas sometimes oversleeps and that an egg laid in 
the fall, if it depended entirely on warmth for its develop- 
ment, might hatch that same season if mild weather should 
continue. And then, what chance would the poor fledgling 
have when a delayed winter comes upon it? None at all, 
of course, and the whole s,cheme for perpetuation of the 
species would be upset. But, if it is so arranged- that 
development within the egg can reach completion only 
after the chilling effect of freezing weather, the emergence 
ot the young insect will be deferred until the return of 
warmth in the spring, and thus the species will have a 
guarantee that its members will not be cut down by unsea- 



sonable hatching. There are, however, species not thus in- 
sured, and these do suffer losses from fall hatching every 
time winter makes a late arrival. Eggs laid in the spring 
are designed to hatch the same season, and the eggs of 
species that live in warm climates never require freezing 
for their development. 

The tough shell of the grasshopper's 
egg is composed of two distinct coats, an 
outer, thicker, opaque one of a pale 
brown color, and an inner one which is 
thin and transparent. Just before hatch- 
ing, the outer coat splits open in an ir- 
regular break over the upper end of the 
egg, and usually half or two-thirds of the 
way down the flat side. This outer coat 
can easily be removed artificially, and 
the inner coat then appears as a glisten- 
ing capsule, through the semitransparent 
walls of which the little grasshopper in- 
side can be seen, its members all tightly 
folded beneath its body. When the 
hatching takes place normally, however, 
both layers of the eggshell are split, and 
the young grasshopper emerges by slowly 
making its way out of the cleft (Fig. 6). 
Newly-hatched grasshoppers that have 
come out of eggs which some meddlesome investigator has 
removed from their pods for observation very soon proceed 
to shed an outer skin from their bodies. This skin, which is 
already loosened at the time of hatching, appears now as a 
rather tightly fitting garment that cramps the soft legs and 
feet of the delicate creature within it. The latter, however, 
after a few forward heaves of the body, accompanied by 
expansions of two swellings on the back of the neck (Fig. 
6), succeeds in splitting the skin over the neck and the 
back of the head, and the pellicle then rapidly shrinks and 
slides down over the body. The insect, thus first exposed, 


Fig. 6. Young grass- 
hopper emerging from 
its eggshell 


liberates itself from the shriveled remnant of its hatching 
skin, and becomes a free new creature in the world. Being 
a grasshopper, it proceeds to jump, and with its first ef- 
forts clears a distance of four or five inches, something like 
fifteen or twenty times the length of its own body. 

When the young locusts hatch under normal undisturbed 
conditions, however, we must picture them as coming out 
of the eggs into the cavernous spaces of the egg pod, and 
all buried in the earth. They are by no means yet free 
creatures, and they can gain their liberty only by burrow- 
ing upward until they come out at the surface of the 
ground. Of course, they are not very far beneath the sur- 
face, and most of the way will be through the easily pene- 
trated walls of the cells of the egg covering. But above the 
latter is a thin layer of soil which may be hard-packed 
after the winter's rains, and breaking through this layer 
can not ordinarily be an easy task. Not many entomolo- 
gists have closely watched the newly-hatched grasshopper 
emerge from the earth, but Fabre has studied them under 
artificial conditions, covered with soil in a glass tube. He 
tells of the arduous efforts the tiny creatures make, press- 
ing their delicate bodies upward through the earth by 
means of their straightened hind legs, while the vesicles on 
the back of the neck alternately contract and expand to 
widen the passage above. All this, Fabre says, is done 
before the hatching skin is shed, and it is only after the 
surface is reached and the insect has attained the freedom 
of the upper world that the inclosing membrane is cast off 
and the limbs are unencumbered. 

The things that insects do and the ways in which they do 
them are always interesting as mere facts, but how much 
wiser might we be if we could discover why they do them ! 
Consider the young locust buried in the earth, for example, 
scarcely yet more than an embryo. How does it know 
that it is not destined to live here in this dark cavity in 
which it first finds itself? What force activates the mech- 
anism that propels it through the earth? And finally, 



what tells the creature that liberty is to be found above, 
and not horizontally or downward? Many people believe 
that these questions are not to be answered by human 
knowledge, but the scientist has faith in the ultimate solu- 
tion of all problems, at least in terms of the elemental 
forces that control the activities of the universe. 

We know that all the activities of animals depend upon 
the nervous system, within which a form of energy resides 
that is delicately responsive to external influences. Any 
kind of energy harnessed to a physical mechanism will 
produce results depending on the con- 
struction of the mechanism. So the ef- 
fects of the nerve force within a living 
animal are determined by the physical 
structure of the animal. An instinctive 
action, then, is the expression of nerve 
energy working in a particular kind of 
machine. It would involve a digression 
too long to explain here the modern con- 
ception of the nature of instinct; it is 
sufficient to say that something in the 
surroundings encountered by the newly- 
hatched grasshopper, or some substance 
generated within it, sets its nerve energy 
into action, that the nerve energy work- 
ing on a definite mechanism produces the 
motions of the insect, and that the 
mechanism is of such a nature that it 
works against the pull of gravity. Hence 
the creature, if normal and healthy in all 
respects, and if the obstacles are not too 
great, arrives at the surface of the ground 
as inevitably as a submerged cork comes 
to the surface of the water. Some 
readers will object that an idea like this destroys the 
romance of life, but whoever wants romance must go to 
the fiction writers; and even romance is not good fiction 

Fig. 7. Eggs of a 
species of katydid at- 
tached to a twig; the 
young insect in suc- 
cessive stages of emerg- 
ing from an egg; and 
the newly-hatched 



unless it represents an effort to portray some truth. 

Insects hatched from eggs laid in the open may begin life 
under conditions a little easier than those imposed upon 
the young grasshopper. Here, for example (Fig. 7), are 
some eggs of insects belonging to the katydid family. 
They look like flat oval seeds stuck in overlapping rows, 
some on a twig, others along the edge of a leaf. When 
about to hatch, each egg splits halfway down one edge and 
crosswise on the exposed flat surface, allowing a flap to 
open on this side, which gives an easy exit to the young 
insect about to emerge. The latter is inclosed in a delicate 
transparent sheath, within which its long legs and an- 
tennae are closely doubled up beneath the body; but when 
the egg breaks open, the sheath splits also, and as the 
young insect emerges it sheds the skin and leaves it within 
the shell. The new creature has nothing to do now but to 
stretch its long legs, upon which it walks away, and, if 
given suitable food, it will soon be contentedly feeding. 

Let us now take closer notice of the little grasshoppers 
(Fig. 8) that have just come into the great world from the 
dark subterranean chambers of their egg-pods. Such an 
inordinately large head surely, you would say, must over- 
balance the short tapering body, though supported on 
three pairs of legs. But, whatever the proportions, nature's 
works never have the appearance of being out of drawing; 
because of some law of recompense, they never give you 
the uneasy feeling of an error in construction. In spite of 
its enormous head, the grasshopper infant is an agile crea- 
ture. Its six legs are all attached to the part of the body 
immediately behind the head, which is known as the 
thorax (Fig. 63, Th), and the rest of the body, called the 
abdomen {Ab), projects free without support. An insect, 
according to its name, is a creature divided into parts, for 
"insect" means "in-cut." A fly or a wasp, therefore, comes 
closer to being the ideal insect; but, while not literally in- 
sected between the thorax and abdomen, the grasshopper, 
like the fly and the wasp and all other insects, consists of a 



head, a thorax bearing the legs, and a terminal abdomen 
(Fig. 63). On the head is located a pair of long, slender 
antennae {Ant) and a pair of large eyes (E). Winged in- 
sects have usually two pairs of wings attached to the back 
of the thorax {Wi, JV 3 ). 

The outside of the insect's body, instead of presenting a 
continuous surface like that of most animals, shows many 
encircling rings where the hard integument appears to be 
infolded, as it really is, dividing each body region except 
the head into a series of short overlapping sections. These 

body sections are called 
segments, and all insects 
and their relatives, in- 
cluding the centipedes, 
the shrimps, lobsters, and 
crabs, and the scorpions 
and spiders, are seg- 
mented animals. The in- 
sect's thorax consists of 
three segments, the first 
of which carries the first 
pair of legs, the second 
the middle pair of legs, and the third the hind pair of legs. 
The abdomen usually consists of ten or eleven segments, 
but generally has no appendages, except a pair of small 
peglike organs at the end known as the cerci, and, in the 
adult female, the prongs of the ovipositor (Fig. 2 B), which 
belong to the eighth and ninth segments. 

The head, besides carrying the antennae (Fig. 63, Ant), 
has three pairs of appendages grouped about the mouth, 
which serve as feeding organs and are known collectively 
as the mouth parts. The presence of four pairs of append- 
ages on the head raises the question, then, as to why the 
head is not segmented like the thorax and the abdomen. 
At an early stage of embryonic growth the head is seg- 
mented, and each pair of its appendages is borne by a 
single segment, but the head segments are later condensed 


Fig. 8. A young grasshopper, or nymph, 
in the second stage after hatching 


into the solid capsule of the cranium. Thus we see that 
the entire body of an insect is composed of a series of seg- 
ments which have become grouped into the three body 
regions. Note that the insect does not have a 
"nose" or any breathing apertures on its head. 
It has, however, many nostrils, called spiracles 
(Fig. 70, Sp), distributed along each side of 
the thorax and the abdomen. Its breathing 
system is quite different from ours, but will 
be described in another chapter treating of 
the internal organization (page 1 14). 

Most young insects grow rapidly be- 
cause they must compress their entire 
lives within the limits of a 
single season. Generally a few \V 
weeks suffice for them to reach 
maturity, or at least the ma- 
ture growth of the form in 
which they leave the egg, for, 
as we shall see, many in- 
sects complicate their lives 
by having several different 
stages, in each of which 
they present quite a dif- 
ferent form. The grass- 
hopper, however, is an in- 
sect that grows by 
a direct course from 
its form at hatch- 
ing to that of the 
adult, and at all 
stages it is recog- 
nizable as a grass- 
hopper (Fig. 9). A 
young moth, on 
the other hand, 
hatching in the 

Fig. 9. The metamorphosis of a grasshopper, 
Melanoplus atlanus, showing its six stages of develop- 
ment from the newly-hatched nymph to the fully- 
winged adult. (Twice natural size) 



form of a caterpillar, has no resemblance to its parent, and 
the same is true of a young fly, which is a maggot, and of 
the grublike young of a bee. The changes of form that 
insects undergo during their growth are known as meta- 
morphosis. There are different degrees of such trans- 
formation; the grasshopper and its relatives have a simple 

An insect differs from a vertebrate animal in that its 
muscles are attached to its skin. Most species of insects 
have the skin hardened by the formation of a strong out- 
side cuticula to give a firm support to the muscles and to 
resist their pull. This function of the cuticula, however, 
imposes a condition of permanency on it after it is once 
formed. As a consequence the growing insect is con- 
fronted with the alternatives, after reaching a certain 
size, of being cramped to death within its own skin, or of 
discarding the old covering and getting a new and larger 
one. It has adopted the course of expediency, and peri- 
odically molts. Thus it comes about that the life of an 
insect progresses by stages separated by the molts, or the 
shedding of the cuticula. 

The grasshopper makes six molts between the time of 
hatching and its attainment of the final adult form, a 
period of about six weeks, and goes through six post- 
embryonic stages (Fig. 9). The first molt is the shedding 
of the embryonic skin, which, we have seen, takes place 
normally as soon as the young insect emerges from the 
earth. The grasshopper now lives uneventfully for about 
a week, feeding by preference on young clover leaves, but 
taking almost any green thing at hand. During this time 
its abdomen lengthens by the extension of the membranes 
between its segments, but the hard parts of the body do 
not change either in size or in shape. At the end of seven 
or eight days, the insect ceases its activities and remains 
quiet for a while until the cuticula opens in a lengthwise 
split over the back of the thorax and on the top of the 
head. The dead skin is then cast off, or rather, the grass- 



hopper emerges from it, carefully pulling its legs and an- 
tennae from their containing sheaths. The whole process 
consumes only a few minutes. The emerged grasshopper 
is now entering its third stage after hatching, but the shed- 
ding of the hatching skin is usually not counted in the 
series of molts, and the first subsequent molt, then, we will 
say, ushers it into its second stage of aboveground life. 
In this state the insect is different in some respects from 
what it was in the first stage: it is not only larger, but the 
body is longer in proportion to the size of the head, as are 
also the antennae, and particularly the hind legs. Again 
the insect becomes active and pursues its routine life for 
another week; then it undergoes a second molting, ac- 
companied by changes in form and proportions that make 
it a little more like a mature grasshopper. After shedding 
its cuticula on three succeeding occasions, it appears in the 
adult form, which it will retain throughout the remainder 
of its life. 

The grasshopper developed its legs, its antennae, and 
most of its other organs while it was in the egg. It was 
hatched, however, without wings, and yet, as everyone 
knows, most full-grown grasshoppers have two pairs of 
wings (Fig. 63, JV 2 , W^), one pair attached to the back of 
the middle segment of the thorax, the other to the third 
segment. It has acquired its wings, therefore, during its 
growth from youth to maturity, and by examining the 
insect in its different stages (Fig. 9), we may learn some- 
thing of how the wings are developed. In the first stage, 
evidence of the coming wings is scarcely apparent, but in 
the second, the lower hind angles of the plates covering the 
back of the second and third thoracic segments are a little 
enlarged and project very slightly as a pair of lobes. In 
the third stage, the lobes have increased in size and may 
now be suspected of being rudiments of the wings, which, 
indeed, they are. At the next molt, when the insect 
enters its fourth stage, the little wing pads are turned 
upward and laid over the back, which disposition not only 



reverses the natural position of the wings, but brings the 
hind pair outside the front pair. At the next molt, the 
wings retain their reversed positions, but they are once 
more increased in size, though they still remain far short 
of the dimensions of the wings of an adult grasshopper. 

At the time of the last molt, the grasshopper takes a 
position with its head downward on some stem or twig, 
which it grasps securely with the claws of its feet. Then, 
when its cuticula splits, it crawls downward out of the 
skin. Once free, however, it reverses its position, and the 
wisdom of this act is seen on observing the rapidly expand- 
ing and lengthening wings, which can now hang down- 
ward and spread out freely without danger of crumpling. 
In a quarter of an hour the wings have enlarged from small, 
insignificant pads to long, thin, membranous fans that 
reach to the tip of the body. This rapid growth is ex- 
plained by the fact that the wings are hollow sacs; their 
visible increase in size is a mere distention of their wrinkled 
walls, for they were fully formed beneath the old cuticula 
and lay there before the molt as little crumpled wads, 
which, when released by the removal of the cases that 
cramped them, rapidly spread out to their full dimensions. 
Their thin, soft walls then come together, dry, and harden, 
and the limp, flabby bags are converted into organs of 

It is important to understand the process of molting as 
it takes place in the grasshopper, because the processes of 
metamorphosis, such as those which accomplish the trans- 
formation of a caterpillar into a butterfly, differ only in 
degree from those that accompany the shedding of the 
skin between any two stages of the grasshopper's life. The 
principal growth of the insect is made during those resting 
periods preceding the molts. It is then that the various 
parts enlarge and make whatever alterations in shape they 
are to have. The old cuticula is already loosened and the 
changes go on beneath it, while at the same time a new 
cuticula is generated over the remodeled surfaces. The 



increased size of the antennae, legs, and wings causes them 
to be compressed in the narrow space between the new and 
the old cuticula, and, when the latter is cast off, the 
crumpled appendages expand to their full size. The ob- 
server then gets the impression that he is witnessing a sud- 
den transformation. The impression, however, is a false 
one; what is really going on is comparable with the display 
of new dresses and coats that the merchant puts into his 
show windows at the proper season for their use, which he 
has just unpacked from their cases but which were pro- 
duced in the factories long before. 

The adult grasshoppers lead prosaic lives, but, like a 
great many good people, they fill the places allotted to 
them in the world, and see to it that there will be other 
occupants of their own kind for these same places when 
they themselves are forced to vacate. If they seldom fly 
high, it is because it is not the nature of locusts to do so; 
and if, in the East, one does sometimes soar above his 
fellows, he accomplishes nothing, unless he happens to 
land on the upper regions of a Manhattan skyscraper, 
when he may attain the glory of a newspaper mention of 
his exploit — most likely, though, with his name spelled 

On the other hand, like all common folk born to ob- 
scurity and enduring impotency as individuals, the grass- 
hopper in masses of his kind becomes a formidable creature. 
Plagues of locusts are of historic renown in countries south 
of the Mediterranean, and even in our own country hordes 
of grasshoppers known as the Rocky Mountain locust did 
such damage at one time in the States of the Middle West 
that the government sent out a commission of entomolo- 
gists to investigate them. This was in the years following 
the Civil War, when, for some reason, the locusts that 
normally inhabited the Northwest, east of the Rocky 
Mountains, became dissatisfied with their usual breeding 
grounds and migrated in great swarms into the States of 
the Mississippi valley, where they brought destruction to 



all kinds of crops wherever they chanced to alight. In 
the new localities they would lay their eggs, and the young 
of the next season, after acquiring their wings, would 
migrate back toward the region whence the parent swarm 
had come the year before. 

The entomologists of the investigating commission in 
the year 1877 tell us that on a favorable day the migrating 
locusts "rise early in the forenoon, from eight to ten 
o'clock, and settle down to eat from four to five in the 
afternoon. The rate at which they travel is variously 
estimated from three to fifteen or twenty miles an hour, 
determined by the velocity of the wind. Thus, insects 
which began to fly in Montana by the middle of July may 
not reach Missouri until August or early September, a 
period of about six weeks elapsing before they reach their 
destined breeding grounds." The appearance of a swarm 
in the air was described as being like that of "a vast body 
of fleecy clouds," or a "cloud of snowflakes," the mass of 
flying insects "often having a depth that reaches from 
comparatively near the ground to a height that baffles 
the keenest eye to distinguish the insects in the upper 
stratum." It was estimated that the locusts could fly 
at an elevation of two and a half miles from the general 
surface of the ground, or 15,000 feet above sea level. The 
descending swarm falls upon the country "like a plague 
or a blight," said one of the entomologists of the com- 
mission, Dr. C. V. Riley, who has left us the following 
graphic picture of the circumstances: 

The farmer plows and plants. He cultivates in hope, watching his 
growing grain in graceful, wave-like motion wafted to and fro by the 
warm summer winds. The green begins to golden; the harvest is at 
hand. Joy lightens his labor as the fruit of past toil is about to be 
realized. The day breaks with a smiling sun that sends his ripening 
rays through laden orchards and- promising fields. Kine and stock 
of every sort are sleek with plenty, and all the earth seems glad. The 
day grows. Suddenly the sun's'face is darkened, and clouds obscure 
the sky. The joy of the morn gives way to ominous fear. The day 
closes, and ravenous locust-swarms have fallen upon the land. The 



morrow comes, and, ah! what a change it brings! The fertile land of 
promise and plenty has become a desolate waste, and old Sol, even at 
his brightest, shines sadlv through an atmosphere alive with myriads 
of glittering insects. 

Even today the farmers of the Middle Western States 
are often hard put to it to harvest crops, especially alfalfa 
and grasses, from fields that are teeming with hungry 
grasshoppers. By two means, principally, they seek relief 
from the devouring hordes. One method is that of driv- 
ing across the fields a device known as a "hopperdozer," 
which collects the insects bodily and destroys them. The 
dozer consists essentially of a long shallow pan, twelve or 
fifteen feet in length, set on low runners and provided with 
a high back made either of metal or of cloth stretched over 
a wooden frame. The pan contains water with a thin 
film of kerosene over it. As the dozer is driven over the 
field, great numbers of the grasshoppers that fly up before it 
either land directly in the pan or fall into it after striking 
the back, and the kerosene film on the water does the rest, 
for kerosene even in very small quantity is fatal to the 
insects. In this manner, many bushels of dead locusts 
are taken often from each acre of an alfalfa field; but still 
great numbers of them escape, and the dozer naturally 
can not be used on rough or uneven ground, in pastures, 
or in fields with standing crops. A more generally effec- 
tive method of killing the pests is that of poisoning them. 
A mixture is prepared of bran, arsenic, cheap molasses, and 
water, sufficiently moist to adhere in small lumps, with 
usually some substance added which is supposed to make 
the "mash" more attractive to the insects. The deadly 
bait is then finely broadcast over the infested fields. 

While such methods of destruction are effective, they 
bear the crude and commonplace stamp of human ways. 
See how the thing is done when insect contends against 
insect. A fly, not an ordinary fly, but one known to 
entomologists as Sarcophaga kellyi (Fig. 10), being 
named after Dr. E. O. G. Kelly, who has given us a 

I 19] 


Fig. io. A fly whose larvae are parasitic on grass- 
hoppers, Sarcophaga kellyi. (Much enlarged) 

description of its habits, frequents the fields in Kansas 
where grasshoppers are abundant. Individuals of this 
flv, according to Doctor Kelly's account, are often seen 

to dart aftergrass- 
hoppers on the 
wing and strike 
against them. 
The stricken in- 
sect at once drops 
to the ground. 
Examination re- 
veals no physical 
injury to the vic- 
tim, but on a close 
inspection there 
may be found ad- 
hering to the un- 
der surface of a 
wing several tiny, soft, white bodies. Poison pills? 
Pellets of infection? Nothing so ordinary. The things 
are alive, they creep along the folds of the wing toward 
its base — they are, in short, young flies born at the instant 
the body of the mother fly struck the wing of the grass- 
hopper. But a young fly would never be recognized as the 
offspring of its parent; it is a wormlike creature, or maggot, 
having neither wings nor legs and capable of moving only 
by extending and contracting its soft, flexible body (Fig. 
182 D). 

In form, the young Sarcophaga kelhi does not differ par- 
ticularly from the maggots of other kinds of flies, but the 
Sarcophaga flies in general differ from most other insects 
in that their eggs are hatched within the bodies of the 
females, and these flies, therefore, give birth to young 
maggots instead of laying eggs. The female of Sarcophaga 
kellyi, then, when she launches her attack on the flying 
grasshopper, is munitioned with a load of young maggots 
ready to be discharged and stuck by the moisture of their 



bodies to the object of contact. The young parasites thus 
palmed off by their mother on the grasshopper, who has no 
idea what has happened to him, make their way to the base 
of the wing of their unwitting host, where they find a ten- 
der membranous area which they penetrate and thereby 
enter the body of the victim. Here they feed upon the 
liquids or tissues of the now helpless insect and grow to 
maturity in from ten to thirty days. Meanwhile, how- 
ever, the grasshopper has died; and when the parasites are 
full grown, they leave the dead body and bury themselves 
in the earth to a depth of from two to six inches. Here 
they undergo the transformation that will give them the 
form of their parents, and when they attain this stage they 
issue from the earth as adult winged flies. Thus, one 
insect is destroyed that another may live. 

Is the Sarcophaga kelhi a creature of uncanny shrewd- 
ness, an ingenious inventor of a novel way for avoiding the 
work of caring for her offspring? Certainly her method 
is an improvement on that of leaving one's newborn prog- 
eny on a stranger's doorstep, for the victim of the fly must 
accept the responsibility thrust upon him whether he will 
or not. But Doctor Kelly tells us that the flies do not 
know grasshoppers from other flying insects, such as 
moths and butterflies, in which their maggots do not find 
congenial hosts and never reach maturity. Furthermore, 
he says, the ardent flv mothers will go after pieces of 
crumpled paper thrown into the wind and will discharge 
their maggots upon them, to which the helpless infants cling 
without hope of survival. Such performances, and many 
similar ones that could be recounted of other insects, show 
that instinct is indeed blind and depends, not upon fore- 
sight, but on some mechanical action of the nervous sys- 
tem, which gives the desired result in the majority of cases 
but which is not guarded against unusual conditions or 

When we consider the many perfected instincts among 
insects, we are often shocked to find apparent cases of 



flagrant neglect on the part of nature for her creatures, 
where it would seem a remedy for their ills would be easy 
to supply. 

In human society of modern times the criminal element 
has come to look no different from the law-abiding class of 
citizens. Formerly, it we may judge from pictures and 
stage representations, thieves and thugs were tough-look- 
ing individuals that could not be mistaken on sight, but 

Fk.. ii. Two blister beetles whose larvae feed on grasshopper 

eggs. (Twice natural size) 

A, Epicauta marginata. B, Epicauta vittata 

today our bandits are spruce young fellows that pass with- 
out suspicion in the crowd. And thus it is with the in- 
sects, all unsuspectingly one may be rubbing elbows with 
another that overnight will despoil his home, or that has 
already committed some act of violence against his neigh- 
bor. Here, for example, in the same field with the grass- 
hoppers, is an innocent-looking beetle, about three- 
quarters of an inch in length, black and striped with yellow 
(Fig. ii B). His entomological name is Epicauta vittata, 
which, of course, means nothing to a locust. He is now 
a vegetarian, but in his younger days he ravished the nest 
of a grasshopper and devoured the eggs, and his progeny 
will do the same again. Epicauta and others of his family 


are known as "blister beetles" because they have a sub- 
stance in their blood, called cantharidin, famous for its 
blistering properties and formerly much used in medicine. 
The female blister beetles of several species lay their eggs 
in the ground in regions frequented by grasshoppers, where 
the young on hatching can find the egg-pods of the latter. 
The little beetles (Fig. 12) hatch in a form quite different 
from that of their parents and are known as triungulins 
because of two spines beside the single claw on each of 
their feet, which gives the foot a three-clawed appearance. 
Though the young scapegrace of a beetle is a housebreaker 
and a thief, his story, like that of too many criminals, 
unfortunately, makes interesting read- 
ing, and the following account is taken, 
with a few omissions, from the history 
of Epicauta vittata as given by Dr. 
C. V. Riley: 

From July till the middle of October the 
eggs are being laid in the ground in loose, irreg- 
ular masses of about 130 on an average — the 
temale excavating a hole tor the purpose, and 
afterwards covering up the mass by scratching 
with her feet. She lays at several different 
intervals, producing in the aggregate probably 
from four to five hundred ova. She prefers for 
purposes of oviposition the very same warm 
sunny locations chosen by the locusts, and 
doubtless instinctively places her eggs near 
those of these last, as I have on several occa- 
sions found them in close proximity. In the 
course of about 10 days — more or less, accord- 
ing to the temperature of the ground — the 
first larva or triungulin hatches. These little 
triungulins (Fig. 12), at first feeble and per- 
fectly white, soon assume their natural light-brown color and commence 
to move about. At night, or during cold or wet weather, all those 
of a batch huddle together with little motion, but when warmed by 
the sun they become very active, running with their long legs over the 
ground, and prying with their large heads and strong jaws into every 
crease and crevice in the soil, into which, in due time, they burrow 


Fir.. 12. The first- 
stage larva, or "triun- 
gulin," of the striped 
blister beetle (fig. II 
B). Enlarged 12 times. 
(From Riley) 


and hide. As becomes a carnivorous creature whose prey must be 
industriously sought, they display great powers of endurance, and 
will survive for a fortnight without food in a moderate temperature. 
Yet in the search for locust eggs many are, without doubt, doomed 
to perish, and only the more fortunate succeed in finding appropriate 

Reaching a locust egg-pod, our triungulin, by chance, or instinct, 
or both combined, commences to burrow through the mucous neck, 
or covering, and makes its first repast thereon. If it has been long 
in search, and its jaws are well hardened, it makes quick work through 
this porous and cellular matter, and at once gnaws away at an egg, 
first devouring a portion of the shell, and then, in the course of two 
or three days, sucking up the contents. Should two or more triun- 
gulins enter the same egg-pod, a deadly conflict sooner or later ensues 
until one alone remains the victorious possessor. 

The surviving triungulin then attacks a second egg and 
more or less completely exhausts its contents, when, after 
about eight days from the time of its hatching, it ceases 
from its feeding and enters a period of 
rest. Soon the skin splits along the 
back, and the creature issues in the 
second stage of its existence. Very 
curiously, it is now quite different in 
appearance, being white and soft-bodied 
and having much shorter legs than 
before (Fig. 13). After feeding again on 
the eggs for about a week, the creature 
molts a second time and appears in a 
still different form. Then once more, 
and yet a fourth time, it sheds its skin 
and changes its form. Just before the 
fourth molt, however, it quits the eggs 
and burrows a short distance into the 
soil, where it composes itself for a 
period of retirement, and here undergoes 
another molt, in which the skin is not cast off. Thus the 
half-grown insect passes the winter, and in spring molts a 
sixth time and becomes active again, but not for long — its 
larval life is now about to close, and with another molt 

Fig. 13. The second- 
stage larva of the 
striped blister beetle. 
(From Riley) 



it changes to a pupa, the stage in which it is to be trans- 
formed back into the form of its beetle parents. The final 
change is accomplished in less than a week, and the 
creature then emerges from the soil, now a fully-formed 
striped blister beetle. 

The grasshoppers' eggs furnish food for many other 
insects besides the young blister beetles. There are species 
of flies and of small wasplike insects whose larvae feed in 
the egg-pods in much the same manner as do the triungu- 
lins, and there are still other species of general feeders 
that devour the locust eggs as a part of their miscellaneous 
diet. Notwithstanding all this destruction of the germs 
of their future progeny, however, the grasshoppers still 
thrive in abundance, for grasshoppers, like most other 
insects, put their trust in the admonition that there is 
safety in numbers. So many eggs are produced and stored 
away in the ground each season that the whole force of 
their enemies combined can not destroy them all, and 
enough are sure to come through intact to render certain 
the continuance of the species. Thus we see that nature 
has various ways of accomplishing her ends — she might 
have given the grasshopper eggs better protection in the 
pods, but, being usually careless of individuals, she chose 
to guarantee perpetuance with fertility. 



Nature's tendency is to produce groups rather than in- 
dividuals. Any animal you can think of resembles in 
some way another animal or a number of other animals. 
An insect resembles on the one hand a shrimp or a crab, 
and on the other a centipede or a spider. Resemblances 
among animals are either superficial or fundamental. For 
example, a whale or a porpoise resembles a fish and lives 
the life of a fish, but has the skeleton and other organs of 
land-inhabiting mammals. Therefore, notwithstanding 
their form and aquatic habits, whales and porpoises are 
classed as mammals and not as fishes. 

When resemblances between animals are of a funda- 
mental nature, we believe that they represent actual blood 
relationships carried down from some far-distant common 
ancestor; but the determination of relationships between 
animals is not always an easy matter, because it is often 
difficult to know what are fundamental characters and 
what are superficial ones. It is a part of the work of 
zoologists, however, to investigate closely the structure of 
all animals and to establish their true relationships. The 
ideas of relationship which the zoologist deduces from his 
studies of the structure of animals are expressed in his 
classification of them. The primary divisions of the 
Animal Kingdom, which is generally likened to a tree, are 
called branches, or phyla (singular, phylum). 

The insects, the centipedes, the spiders, and the shrimps, 
crayfish, lobsters, crabs, and other such creatures belong to 
the phylum Arthropoda. The name of this phylum means 



"jointed-legs"; but, since many other animals have jointed 
legs, the name is not distinctive, except in that the legs of 
the arthropods are particularly jointed, each being com- 
posed of a series of pieces that bend upon each other in 
different directions. A name, however, as everybody 
knows, does not have to mean anything, for Mr. Smith 

l'li.. 14. Kxamples of four common classes of the Arthropoda 

A, a crab (Crustacea). B, a spider (Arachnida). C, a centipede (Chilopoda). 

D, a fly (Insecta, or Hexapoda) 

may be a carpenter, and Mr. Carpenter a smith. A phylum 
is divided into classes, a class into orders, an order into 
families, a family \nto genera (singular, genus), and a genus 
is composed of species (the singular of which is also species). 
Species are hard to define, but they are what we ordinarily 
regard as the individual kinds of animals. Species are 
given double names, first the genus name, and second a 
specific name. For example, species of a common grass- 
hopper genus named Melanoplus are distinguished as 
Melanoplus atlanus, Melanoplus femur-rubrum, Melanoplus 
differentia/is, etc. 

[ 27 ] 


The insects belong to the class of the Arthropoda known 
as the Insecta, or Hexapoda. The word "insect," as we 
have seen, means "in-cut," while "hexapod" means "six- 
legged" — either term, then, doing very well for insects. 
The centipedes (Fig. 14 C) are the Myriapoda, or many- 
footed arthropods; the crabs (A), shrimps, lobsters, and 
others of their kind are the Crustacea, so called because 
most of them have hard shells; the spiders (B) are the 
Arachnida, named after that ancient Greek maiden so 
boastful of her spinning that Minerva turned her into a 
spider; but some arachnids, such as the scorpion, do not 
make webs. 

The principal groups of insects are the orders. The 
grasshopper and its relatives constitute an order; the 
beetles are an order; the moths and butterflies are another 
order; the flies another; the wasps, bees, and ants still 
another. The grasshopper's order is called the Orthoptera, 
the word meaning "straight-wings," but, again, not sig- 
nificant in all cases, though serving very well as a name. 
The order is a group of related families, and, in the Or- 
thoptera, the grasshoppers, or locusts, make one family, 
the katydids another, the crickets a third; and all these in- 
sects, together with some others less familiar, may be said 
to be the grasshopper's cousins. 

The orthopteran families are notable in many ways, 
some for the great size attained by their members, some 
for their remarkable forms, and some for musical talent. 
While this chapter will be devoted principally to the 
cousins of the grasshopper, a few things of interest may 
still be said about the grasshopper himself, in addition to 
what was given in the preceding chapter. 

The Grasshopper Family 

The family of the grasshoppers, or locusts, is the 
Acrididae. All the members are much alike in form and 
habits, though some have long wings and some short wings, 
and some reach the enormous size of nearly six inches in 



A group of insects representing five common entomological Orders. 
Figure 1 is a damselfly, a kind of dragonfly, from New Guinea, Order 
Odonata; 4 is a grasshopper, and 6 a winged walking-stick of Japan, 
representing two families of Orthoptera; I and 8 are sucking bugs, 
Order Hemiptera, which includes also the aphids and the cicadas; 
3 is a wasp from Paraguay, and 7 a solitary bee from Chile, Order 
Hymenoptera; 5 is a two-winged fly of the Order Diptera, from Japan. 
To entomologists these insects are known as follows : I, Paryphes 
laettts; 2, unidentified; 3, Pepsis completa; 4, Heliastus benjamini; K, 
Pantophthalmus vittatus; 6, Micadina phluctanoides; 7, Caupolicana 
fulvicollis; 8, Margasus qfzeli 


length. The front wings are long and narrow (Fig. 63, 
fVi), somewhat stiff, and of a leathery texture. They are 
laid over the thinner hind wings as a protection to the 
latter when the wings are folded over the back, and for 
this reason they are called the tegmina (singular, legmen). 
The hind wings, when spread (IV-i), are seen to be large 
tans, each with many ribs, or veins, springing from the 
base. These wings are gliders rather than organs of flight. 
For most grasshoppers leap into the air by means of 
their strong hind legs and then sail off on the outspread 
wings as far as a weak fluttering of the latter will 
carry them. One of our common species, however, the 
Carolina locust (Frontispiece), is a strong flyer, and when 

Fig. 15. A grasshopper, Chloeallis conspersa, that makes a sound by scraping 

its hind thighs over sharp-edged veins of its wings 

A, the male grasshopper, showing the sound-making veins of the wing {b). B, 

inner surface of right hind leg, showing row of teeth (a) on the lemur. C, 

several teeth of the femur (enlarged* 

flushed flits away on an undulating course over the 
weeds and bushes and sometimes over the tops of small 
trees, but always swerving this way and that as it unde- 
cided where to alight. The great flights of the migratory 
locusts, described in the last chapter, are said to have been 
accomplished more by the winds than by the insects' 
Strength of wing. 

The locusts are distinguished by the possession of large 



organs on the sides of the body that appear to be designed 
for purposes of hearing. No insect, of course, has "ears" 
on its head; the grasshopper's supposed hearing organs are 
located on the base of the abdomen, one on each side 
(Fig. 63, Trri). Each consists of an oval depression of the 
body wall with a thin eardrumlike membrane, or tympa- 
num, stretched over it. Air sacs lie against the inner face 
of the membrane, furnishing the equilibrium of air pressure 
necessary for free vibration in response to sound waves, 
and a complicated sensory apparatus is attached to its 
inner wall. Even with such large ears, however, attempts 
at making the grasshopper hear are never very successful; 
but its tympanal organs have the same structure as those 
of insects noted for their singing, which presumably, 
therefore, can hear their own sound productions. 

Not many of the grasshoppers are muscial. They are 
mostly sedate creatures that conceal their sentiments, if 
they have any. They are awake in the daytime and they 
sleep at night — commendable traits, but habits that seldom 
beget much in the way of artistic attainment. Yet a few 
of the grasshoppers make sounds that are perhaps music 
in their own ears. One such is an unpretentious little 
brown species (Fig. 15) about seven-eighths of an inch in 
length, marked by a large black spot on each side of the 
saddlelike shield that covers his back between the head and 
the wings. He has no other name than his scientific one of 
Chloealtis conspersa, for he is not widely known, since his 
music is of a very feeble sort. According to Scudder, his 
only notes resemble tsikk-tsikk-tsikk, repeated ten or twelve 
times in about three seconds in the sun, but at a slightly 
lower rate in the shade. Chloealtis is a fiddler and plays 
two instruments at once. The fiddles are his front wings, 
and the bows his hind legs. On the inner surface of each 
hind thigh, ox femur, there is a row of minute teeth (Fig. 
15 B, a), shown more magnified at C. When the thighs 
are rubbed over the edges of the wings, their teeth scrape 
on a sharp-edged vein indicated by b. This produces the 



tsikk-sound just mentioned. Such notes contain little 
music to us, but Scudder says he has seen three males sing- 
ing to one female at the same time. This female, however, 

Fig. 16. A grasshopper, Mecostelhus gracilis, that makes a sound 
by scraping sharp ridges on the inner surfaces of its hind thighs 

over toothed veins of the wings 

A, the male grasshopper. B, left front wing; the rasping vein is 

the one marked /. C, a part of the rasping vein and its branches 

more enlarged, showing rows of teeth 

was busy laying her eggs in a near-by stump, and there is 
no evidence given to show that even she appreciated the 
efforts of her serenaders. 

Several other little grasshoppers fiddle after the manner 
of Chloealtis; but another, Mecostethus gracilis by name 
(Fig. 16), instead of having the rasping points on the legs, 
has on each fore wing one vein (B, /) and its branches pro- 
vided with many small teeth, shown enlarged at C, upon 
which it scrapes a sharp ridge situated on the inner sur- 
face of the hind thigh. 

In another group of grasshoppers there are certain 
species that make a noise as they fly, a crackling sound 



apparently produced in some way by the wings themselves. 
One of these, common through the Northern States, is 
known as the cracker locust, Circotettix verruculatus, on 
account of the loud snapping notes it emits. Several 
other members of the same genus are also cracklers, the 
noisiest being a western species called C. carlingianus. 
Scudder says he has had his attention drawn to this grass- 
hopper "by its obstreperous crackle more than a quarter of 
a mile away. In the arid parts of the West it has a 
great fondness for rocky hillsides and the hot vicinity of 
abrupt cliffs in the full exposure to the sun, where its 
clattering rattle re-echoes from the walls." 

The Katydid Family 

While the grasshoppers give examples of the more 
primitive attempts of insects at musical production and 
may be compared in this respect to the more primitive of 
human races, the katydids show the highest development 
of the art attained by insects. But, just as the accom- 
plishments of one member of a human family may give 
prestige to all his relations and descendants, so the talent 
of one noted member of the katydid family has given 
notoriety to all his congeners, and his justly deserved 
name has come to be applied by the undiscriminating 
public to a whole tribe of singers of lesser or very mediocre 
talent whose only claim to the name of katydid is that of 
family relationship. In Europe the katydids are called 
simply the longhorn grasshoppers. In entomology the 
family is now the Tettigoniidae, though it had long been 
known as the Locustidae. 

The katydids in general are most easily distinguished 
from the locusts, or shorthorn grasshoppers, by the great 
length of their antennae, those delicate, sensitive, tapering 
threads projecting from the forehead. But the two fami- 
lies differ also in the number of joints in their feet, the 
grasshoppers having three (Fig. 17 A) and the katydids 
four (B). The grasshoppers place the entire foot on the 




ground, while the katydids ordinarily walk on the three 
basal segments only, carrying the long terminal joint 
elevated. The basal segments have pads on their under 
sides that adhere to any smooth surface such as that of a 
leaf, but the terminal joint bears a pair of claws used 
when it is necessary to grasp the edge of a support. The 
katydids are mostly creatures of the night and, though 
usually plain green in color, many of them have elegant 
forms. Their attitudes and general 
comportment suggest much more re- 
finement and a higher breeding than 
that of the heavy-bodied locusts. 
Though some members of the katydid A 

family live in the fields and are very s ^>- 
grasshopperlike or even cricketlike ^\>=— ^-^^^^^S) 
in form and manners, the character- vb$p-f*§C_S 
istic species are seclusive inhabitants 
of shrubbery or trees. These are the (\{*r~ 
true aristocrats of the Orthoptera. 

An insect musician differs in many 
respects from a human musician, 
aside from that of being an insect in- 
stead of a human being. The insect 
artists are all instrumentalists; but 
since the poets and other ignorant 
people always speak of the "singing" 
of the crickets and katydids, it will be 
easier to use the language of the public than to correct it, 
especially since we have nothing better to offer than the 
word stridulating, a Latin derivative meaning "to creak." 
But words do not matter if we explain what we mean by 
them. It must be understood, therefore, that though we 
speak of the "songs" of insects, insects do not have true 
voices in the sense that "voice" is the production of sound 
by the breath playing on vocal cords. All the musical 
instruments of insects, it is true, are parts of their bodies; 
but they are to be likened to fiddles or drums, since, for the 



Fig. 17. Distinctive char- 
acters in the feet of the 
three families of singing 

A, hind foot of a grass- 
hopper. B, hind foot of a 
katydid. C, hind foot of 

a cricket 


production of sound, they depend upon rasping and vibrat- 
ing surfaces. The rasping surfaces are usually, as in the 
instruments of the grasshoppers (Figs. 15, 16), parts of 
the legs and the wings. The sound may be intensified, as 
in the body of a stringed instrument, by special resonating 

areas, sometimes on 
the wings, sometimes 
on the body. The 
cicadas, a group of 
musical insects to be 
described in a special 
chapter, have large 
drumheads in the wall 
of the body with 
which they produce 
their shrill music. 
They do not beat 
these drums, but 
cause them to vibrate 
by muscles in the 
body. The musical 
members of the insect 
families are in nearly 
all cases the males, 
and it is usually sup- 
posed that they give 
their concerts for the 
purpose of engaging 
the females, but that 
this is so in all cases 
we can not be certain. 
The musical instru- 
ments of the katydids 
are quite different 
from those of the 
grasshoppers, being 
situated on the over- 

Fig. 18. The front wings, or tegmina, of a 

meadow grasshopper, Orchelimum laticauda, 

illustrating the sound-making organs typical 

of the katydid family 

A, left front wing and basal part of right wing 
of male, showing the four main veins: subcosta 
(Sc), radius (/?), media (M), and cubitus (C«); 
also the enlarged basal vibrating area, or 
tympanum {Tm), of each wing, the thick file 
vein (ft) on the left, and the scraper (s) on 

the right 

B, lower surface of base of left wing of male, 
showing the file if) on under side of the file 

vein (A,fo) 

C, right front wing of female, which has no 
sound-making organs, showing simple normal 




lapping bases ot the front wings, or tegmina. On this 
account the front wings of the males are always different 
from those of the females, the latter retaining the usual or 
primitive structure. The right wing of a female in one of 
the more grasshopperlike species, Orchelimum laticauda 
(Fig. 30), is shown at C of Figure 18. The wing is trav- 
ersed by four principal veins springing from the base. 
The one nearest the inner 
edge is called the cubitus ^~ 
{Cu) and the space be- 
tween it and this margin 
of the wing is filled with 
a network of small veins 
having no particular ar- 
rangement. In the wings 
of the male, however, 
shown at A of the same 
figure, this inner basal 
field is much enlarged 
and consists of a thin, 
crisp membrane (Tm), 
braced by a number of 
veins branching from the 
cubitus (Cu). One of 
these ifv), running cross- 
wise through the mem- 
brane, is very thick on 
the left wing, and when 
the wing is turned over 
(B) it is seen to have a 
close series of small cross- 
ridges on its under sur- 
face which convert it into 

a veritable file (/). On the right wing this same vein is 
much more slender and its file is very weak, but on the 
basal angle of this wing there is a stiff ridge (s) not de- 
veloped on the other. The katydids always fold the 

Fig. 19. Wings, sound-making organs, 
and the "ears" of a conehead grasshopper, 
Neoconocephalus ensiger, a member of the 

katydid family 
A, B, right and left wings, showing the 
scraper {s) on the right, and the file vein 
(/») on the left. C, under surface of the 
file vein, showing the file (/). D, front 
leg, showing slits (e) on the tibia opening 
into pockets containing the hearing 
organs (fig. 20 A) 



wings with the left overlapping the right, and in this position 
the file of the former lies above the ridge (s) of the latter. 
I f now the wings are moved sidewise, thejile grating on the 
ndge or scraper causes a rasping sound, and this is the way 
the katydid makes the notes of its music. The tone and 
volume of the sound, however, are probably in large part 
produced by the vibration of the thin basal membranes of 
the wings, which are called the tympana (Tm). 

The instruments of different players differ somewhat in 
the details of their structure. There are variations in the 
form and size of the file and the scraper on the wings of dif- 
ferent species, and differences in the veins supporting the 
tympanal areas, as shown in the drawings of these parts 
from a conehead (Fig. 27) given at A, B, and C, of Figure 
19. In the true katydid, the greatest singer of the family, 
the file, the scraper, the tympana, and the wings them- 
selves (Fig. 26) are all very highly developed to form an 
instrument of great efficiency. But, in general, the instru- 
ments of different species do not differ nearly so much as 
do the notes produced from them by their owners. An 
endless number of tunes may be played upon the same 
riddle. With the insects each musician knows only one 
tune, or a few simple variations of it, and this he has in- 
herited from his ancestors along with a knowledge of how 
to play it on his inherited instrument. The stridulating 
organs are not functionally developed until maturity, and 
then the insect forthwith plays his native air. He never 
disturbs the neighbors with doleful notes while learning. 

Very curiously, none of the katydids nor any member of 
their family ha; the earlike organs on the sides of the body 
possessed by the locusts. What are commonly supposed 
to be their organs of hearing are located in their front legs, 
as are the similar organs of the crickets. Two vertical 
slits on the upper parts of the shins, or tibiae (Fig. 19 D, e), 
open each into a small pocket (Fig. 20 A, E) with a tym- 
panumlike membrane {Tm) stretched across its inner wall. 
Between the membranes are air cavities (Tra) and a com- 



plicated sensory receptive apparatus (B) connected by a 
nerve through the basal part of the leg with the central 
nervous system. 

There are several groups of katydids, classed as sub- 





Fig. 20. The probable auditory organ of the front leg of Dectkus, 
a member o( the katydid family. (Simplified from Schwabe) 

A, cross-section of the leg through the auditory organ, showing 
the ear slits (e, e) leading into the large ear cavities (E, E) with 
the tympana (Tm, Tm) on their inner faces. Between the 
tympana are two tracheae {Tra. Tra) dividing the leg cavity into 
an upper and a lower channel {BC, BC). The sensory apparatus 
forms a crest on the outer surface of the inner trachea, each ele- 
ment consisting of a cap cell (CCl), an enveloping cell (EC/) con- 
taining a sense rod (Sco), and a sense cell (SC/). Ct, the thick 

cuticula forming the hard wall of the leg 

B, surface view of the sensory organ, showing the elements 
graded in size from above downward. The sense cells (SCt) are 

attached to the nerve (Nv) along the inner side of the leg 

families. A subfamily name ends in inae to distinguish it 
from a family name, which, after the Latin fashion, termi- 
nates in idae. 


The members of this first group of the katydid family 
are characterized by having large wings and a smooth 



round forehead. They compose the subfamily Phanerop- 
terinae, which includes species that attain the acme of 
grace, elegance, and refinement to be found in the entire 
orthopteran order. Nearly all the round-headed katydids 
are musical to some degree, but their productions are not 

Flo. 11. A bush katydid, Scutldtria furcata 

Upper figure, a male; lower, a female in the act of cleaning a 

hind foot 

of a high' order. On the other hand, though their notes 
are in a high key, they are usually not loud and not of the 
kind that keep you awake at night. 

Among this group are the bush katydids, the species of 
which are of medium size with slenderer wings than the 
others, and are comprised in the genus usually known as 
Scudderia but also called Phaneroptera. They have ac- 
quired the name of bush katydids because they are usually 
found on low shrubbery, particularly along the edges of 
moist meadows, though they inhabit other places, too, and 
their notes are often heard at night about the house. Our 



commonest species, and one that occurs over most of the 
United States, is the fork-tailed bush katydid (Scudderia 
furcata). Figure 21 shows a male and a female, the female 
in the act of cleaning the pads on one of her hind feet. The 
katydids are all very particular about keeping their feet 
clean, for it is quite essential to have their adhesive pads 
always in perfect working order; but they are so con- 
tinually stopping whatever they may be doing to lick one 
foot or another, like a dog scratching fleas, that it looks 
more like an ingrown habit with them than a necessary act 
of cleanliness. The fork-tailed katydid is an unpreten- 
tious singer and has only one note, a high-pitched zeep re- 
iterated several times in succession. But it does not re- 
peat the series continuously, as most other singers do, and 
its music is likely to be lost to human ears in the general 
din from the jazzing bands of crickets. Yet occasionally 
its soft zeep, zeep, zeep may be heard from a near-by bush 
or from the lower branches of a tree. 

The notes of other species have been described as zikk, 
zikk, zikk, or zeet, zeet, zeet, and some observers have re- 
corded two notes for the same species. Thus Scudder says 
that the day notes and the night notes of Scudderia curvi- 
cauda differ considerably, the day note being represented 
by bzrwi, the night note, which is only half as long as the 
other, by tchw. (With a little practice the reader should 
be able to give a good imitation of this katydid.) Scudder 
furthermore says that they change from the day note to 
the night note when a cloud passes over the sun as they are 
singing by day. 

The genus Amblycorypha includes a group of species hav- 
ing wider wings than those of the bush katydids. Most of 
them are indifferent singers; but one, the oblong-winged 
katydid (A. oblongifolia), found over all the eastern half of 
the United States and southern Canada, is noted for its 
large size and dignified manners. A male (Fig. 22), kept 
by the writer one summer in a cage, never once lost his 
decorum by the humiliation of confinement. He lived ap- 



parently a natural and contented life, feeding on grape 
leaves and on ripe grapes, obtaining the pulp of the latter 
by gnawing holes through the skin. He was always sedate, 
always composed, his motions always slow and deliberate. 
In walking he carefully lifted each foot and brought the leg 
forward with a steady movement to the new position, 

Fie. 22. The oblong-winged katydid, Amblycorypha oblongifolia, male 

where the foot was carefully set down again. Only in the 
act of jumping did he ever make a quick movement of any 
sort. But his preparations for the leap were as calm and 
unhurried as his other acts: pointing the head upward, 
dipping the abdomen slowly downward, the two long hind 
legs bending up in a sharp inverted V on each side of the 
body, he would lead one to think he was deliberately pre- 
paring to sit down on a tack; but, all at once, a catch 
seems to be released somewhere as he suddenly springs 
upward into the leaves overhead at which he had taken 
such long and careful aim. 

For a long time the aristocratic prisoner uttered no 
sound, but at last one evening he repeated three times a 



squeaking note resembling shriek with the s much aspi- 
rated and with a prolonged vibration on the ie. The next 
evening he played again, making at first a weak swish, 
swish, swish, with the s very sibilant and the i very vibra- 
tory. But after giving this as a prelude he began a sh ill 
shrie-e-e-e-k, shrie-e-e-e-k, repeated six times, a loud 
sound described by Blatchley as a "creaking squawk — like 
the noise made by drawing a fine-toothed comb over a 
taut string." 

The best-known members of the round-headed katydids, 
and perhaps of the whole family, are the angular-winged 
katydids (Fig. 23). These are large, maple-leaf green in- 
sects, much flattened from side to side, with the leaflike 
wings folded high over the back and abruptly bent on their 
upper margins, giving the creatures the humpbacked ap- 
pearance from which they get their name of angular- 
winged katydids. The sloping surface of the back in front 
of the hump makes a large flat triangle, plain in the female, 
but in the male corrugated and roughened by the veins of 
the musical apparatus. 

There are two species of the angular-winged katydids in 
the United States, both belonging to the genus Microcen- 
trum, one distinguished as the larger angular-winged katy- 
did, M. rhombifolium, and the other as the smaller angu- 
lar-winged katydid, M. retinerve. The females of the 
larger species (Fig. 23), which is the more common one, 
reach a length of 2^8 inches measured to the tips of the 
wings. They lay flat, oval eggs, stuck in rows overlapping 
like scales along the surface of some twig or on the edge 
of a leaf. 

The angular-winged katydids are attracted to lights and 
may frequently be found on warm summer nights in the 
shrubbery about the house, or even on the porch and the 
screen doors. Members of the larger species usually make 
their presence known by their soft but high-pitched notes 
resembling tzeet uttered in short series, the first notes re- 
peated rapidly, the others successively more slowly as the 



tone becomes also less sharp and piercing. The song 
may be written tzeet-tzeet-tzeet-tzeet-tzek-tzek-tzek-tzuk-tzuk, 
though the high key and shrill tones of the notes must be 

Fig. 23. The larger angular-winged katydid, Microcentrum rhombijolium 
Upper figure, a male; lower, a female 

imagined. Riley describes the song as a series of raspings 
"as of a stiff quill drawn across a coarse file," and Allard 



says the notes "are sharp, snapping crepitations and sound 
like the slow snapping of the teeth of a stiff comb as some 
object is slowly drawn across it." He represents them 
thus: tek-ek-ek-ek-ek-ek-ek-ek-ek-ek-ek-tzip. But, however 
the song of Microcentrum is to be translated into English, 
it contains no suggestion of the notes of his famous cousin, 
the true katydid. Yet most people confuse the two species, 
or rather, hearing the one and seeing the other, they draw 
the obvious but erroneous conclusion that the one seen 
makes the sounds that are heard. 

The smaller angular-winged katydid, Microcentrum reti- 
nerve, is not so frequently seen as the other, but it has simi- 
lar habits, and may be heard in the vines or shrubbery 
about the house at night. Its song is a sharp zeet, zeet, zeet, 
the three syllables spaced as in ka-ty-did, and it is probable 
that many people mistake these notes tor those of the true 

The angular-winged katydids are very gentle and un- 
suspicious creatures, allowing themselves to be picked up 
without any attempt at escaping. But they are good 
flyers, and when launched into the air sail about like minia- 
ture airplanes, with their large wings spread out straight 
on each side. When at rest they have a comical habit of 
leaning over sidewise as if their flat forms were top-heavy. 


We now come to that artist who bears by right the name 
of "katydid," the insect (Fig. 24) known to science as 
Pterophylla camellifolia and to the American public as the 
greatest of insect singers. Whether the katydid is really a 
musician or not, of course, depends upon the critic, but of 
his fame there can be no question, tor his name is a house- 
hold term as familiar as that of any of our own great 
artists, notwithstanding that there is no phonographic 
record of his music. To be sure, the cicada has more of a 
world-wide reputation than the katydid, for he has repre- 
sentatives in many lands, but he has not put his song into 



words the public can understand. And if simplicity be the 
test of true art, the song of the katydid stands the test, for 
nothing could be simpler than merely katy-did, or its easy 
variations, such as katy, katy-she-did, and katy-didnt. 

Yet though the music of the katydid is known by ear or 
by reputation to almost every native American, few of us 

Fig. 24. The true katydid, Pterophylla camellifolia, a male 

are acquainted with the musician himself. This is because 
he almost invariably chooses the tops of the tallest trees for 
his stage and seldom descends from it. His lofty platform, 
moreover, is also his studio, his home, and his world, and 
the reporter who would have a personal interview must be 
efficient in tree climbing. Occasionally, though, it happens 
that a singer may be located in a smaller tree where access 
to him is easier or from which he may be dislodged by 
shaking. A specimen, secured in this way on August 12, 
lived till October 18 and furnished material for the follow- 
ing notes: 

The physical characters of the captive and some of his 
attitudes are shown in Figures 24 and 25. His length is 
\$i inches from the forehead to the tips of the folded 
wings; the front legs are longer and thicker than in most 
other members of the family, while the hind legs are un- 
usually short. The antennae, though, are extremely long, 
slender, and very delicate filaments, 2 u /i6 inches in length. 



Fig. 25. The katydid in various attitudes 

A, usual position of a male while singing. B, attitude while running rapidly on 

a smooth surface. C, preparing to leap from a vertical surface. D, a male, 

seen from above) showing the stridulating area at the base of the wings. E, a 

female, showing the broad, flat, curved ovipositor 



Between the bases of the antennae on the forehead there 
is a small conical projection, a physical character which 
separates the true katydid from the round-headed katy- 
dids and assigns him to the subfamily called the Pseudo- 
phyllinae, which includes, besides our species, many others 
that live mostly in the tropics. The rear margins of the 
wings are evenly rounded and their sides strongly bulged 
outward as if to cover a very plump body, but the space 
between them is mostly empty and probably forms a 
resonance chamber to give tone and volume to the sound 
produced by the stridulating parts. What might be the 
katydid's waistcoat, the part of the body exposed beneath 
the wings, has a row of prominent buttonlike swellings 
along the middle which rhythmically heave and sink with 
each respiratory movement. All the katydids are deep 
abdominal breathers. 

The color of the katydid is plain green, with a conspicu- 
ous dark-brown triangle on the back covering the stridulat- 
ing area of the wings. The tips of the mouth parts are 
yellowish. The eyes are of a pale transparent green, but 
each has a dark center which, like the pupil in a painting, is 
always fixed upon you from whatever angle you retreat. 

The movements of the captive individual are slow, 
though in the open he can run rather rapidly, and when he 
is in a hurry he often takes the rather absurd attitude 
shown at B of Figure 25, with the head down and the 
wings and body elevated. He never flies, and was never 
seen to spread his wings, but when making short leaps the 
wings are slightly fluttered. In preparing for a leap, if 
only one of a few inches or a foot, he makes very careful 
preparations, scrutinizing the proposed landing place long 
and closely, though perhaps he sees better in the dark and 
acts then with more agility. If the leap is to be made 
from a horizontal surface, he slowly crouches with the legs 
drawn together, assuming an attitude more familiar in a 
cat; but, if the jump is to be from a vertical support, he 
raises himself on his long front legs as at C of Figure 25, 

[46 J 


suggesting a camel browsing on the leaves of a tree. He 
sparingly eats leaves of oak and maple supplied to him in 
his cage, but appears to prefer fresh fruit and grapes, and 
relishes bread soaked in water. He drinks rather less than 
most orthopterons. 

When the katydids are singing at night in the woods they 
appear to be most wary of disturbance, and often the voice 
of a person approaching or a crackle underfoot is sufficient 
to quiet a singer far overhead. The male in the cage never 
utters a note until he has been in darkness and quiet for a 
considerable time. But when he seems to be assured of 
solitude he starts his music, a sound of tremendous volume 
in a room, the tones incredibly harsh and rasping at close 
range, lacking entirely that melody they acquire with space 
and distance. It is only by extreme caution that the per- 
former may be approached while singing, and even then 
the brief flash of a light is usually enough to silence those 
stentorian notes. Yet occasionally a glimpse may be had 
of the musician as he plays, most frequently standing head 
downward, the body braced rather stiffly on the legs, the 
front wings only slightly elevated, the tips of the hind 
wings projecting a little from between them, the abdomen 
depressed and breathing strongly, the long antennal 
threads waving about in all directions. Each syllable ap- 
pears to be produced by a separate series of vibrations 
made by a rapid shuffling of the wings, the middle one be- 
ing more hurried and the last more conclusively stressed, 
thus producing the sound so suggestive of ka-tv-did', ka-ty- 
did', which is repeated regularly about sixty times a minute 
on warm nights. Usually at the start, and often for some 
time, only two notes are uttered, ka-ty, as if the player has 
difficulty in tailing at once into the full swing of ka-tv-did. 

The structure of the wings and the details of the stridu- 
lating parts are shown in Figure 26. The wings (A, B) fold 
vertically against the sides of the body, but their inner 
basal parts form wide, stiff, horizontal, triangular flaps that 
overlap, the left on top of the right. A thick, sunken, 



crosswise vein (fv) at the base of the left tympanum (Tm) is 
the file vein. It is shown from below at C where the 
broad, heavy file (/) is seen with its row of extremely 
coarse rasping ridges. The same vein on the right wing 
(B) is much smaller and has no file, but the inner basal 
angle ot the tympanum is produced into a large lobe bear- 
ing a strong scraper (s) on its 

The quality of the katy- 
did's song seems to differ 
somewhat in different parts 
of the country. In the vicin- 
ity of Washington, the in- 
sects certainly say ka-ty-did 
as plainly as any insect could. 
Of course, the sound is more 
literally to be represented as 
ka ki-kak', accented on the 
last syllable. When only two 
syllables are pronounced they 
are always the first two. 
Sometimes an individual in a 
band utters four syllables, 
"katy-she-did" or ka ki-ka- 
kak\ and again a whole band 

Fig. 26. Wings and the sound-mak- IS heard Singing ill four HOtes 

ing organs of the male katydid w j tn un Iy an Occasional 

A, left front wing, showing the greatly ; „ ■ ; _ .v 1. ■ 1 

enlarged tympanal area {Tm), with its S,11 g er g 1VI11 g f nree - ' * »» Said 

thick file vein (/»). B, base of right that in certain parts of the 

fore wing, with large scraper (j) on its o ^L ^L 1 j'j • 11 j 

inmr angle, but with a very small file S ° Uth the Katydid IS Called 

vein. C, under surface of file vein of a " Cackle - lack," a name 

left wing, showing the large, flat, 1 • 1 " 1 1 ■ 1 

coarsely-ribbed file (f) which, it must be admitted, 

is a very literal translation of 
the notes, but one lacking in sentiment and unbefitting an 
artist of such repute. In New England, the katydids 
heard by the writer in Connecticut and in the western 
part of Massachusetts uttered only two syllables much 



more commonly than three, and the sounds were extremely 
harsh and rasping, being a loud squa-wak 1 ', squa-wak', 
squa-wak', the second syllable a little longer than the first. 
This is not the case with those that sry ka-tv. When there 
were three syllables the series was squa-wa-wak' . If all 
New England katydids sing thus, it is not surprising that 
some New England writers have failed to see how the 
insects ever got the name of "katydid." Scudder says 
"their notes have a shocking lack of melody"; he rep- 
resents the sound by xr, and records that the song is 
usually of only two syllables. "That is," he says, " they 
rasp their fore wings twice rather than thrice; these 
two notes are of equal (and extraordinary) emphasis, the 
latter about one-quarter longer than the former; or if three 
notes are given, the first and second are alike and a little 
shorter than the last." 

When we listen to insects singing, the question always 
arises of why they sing, and we might as well admit that 
we do not know what motive impels them. It is prob- 
ably an instinct with males to use their stridulating organs, 
but in many cases the tones emitted are clearly modified by 
the physical or emotional state of the player. The music 
seems in some way to be connected with the mating of the 
sexes, and the usual idea is that the sounds are attractive 
to the females. With many of the crickets, however, the 
real attraction that the male has for the female is a liquid 
exuded on his back, the song apparently being a mere ad- 
vertisement of his wares. In any case the ecstacies of love 
and passion ascribed to male insects in connection with 
their music are probably more fanciful than real. The 
subject is an enchanted field wherein the scientist has 
most often weakened and wandered from the narrow 
path of observed facts, and where he has indulged in a free- 
dom of imagination permissible to a poet or to a newspaper 
reporter who wishes to enliven his chronicle of some event 
in the daily news, but which does not contribute anything 
substantial to our knowledge of the truth. 




This group o{ the katydid family contains slender, 
grasshopperlike insects that have the forehead produced 

into a large 
cone and the 
face strongly 
receding, but 
which also pos- 
sess long, slen- 
der antennae 
that distinguish 
them from the 
true or short- 
horn grasshop- 
pers. They con- 
stitute the sub- 
family Copi- 

One of the 
commonest and 
most widely 
distributed of 
the larger cone- 
heads is the 
species known as Neoconocephalus ensiger, or the "sword- 
bearing conehead." It is the female, however, that carries 
the sword; and it is not a sword either, but merely the 
immensely long egg-laying instrument properly called the 
ovipositor. The female conehead shown at B of Figure 27, 
has a similar organ, though she belongs to a species called 
retusus. The two species are very similar in all respects 
except for slight differences in the shape of the cone on the 
head. They look like slim, sharp-headed grasshoppers, 
1 X A to \)4, inches in length, usually bright green in color, 
though sometimes brown. 


Fig. 27. A conehead grasshopper, or katydid, Neocono- 
cephalus retusus 
Upper figure, a male; lower, a female, with extremely long 


The song of ensiger sounds like the noise of a miniature 
sewing machine, consisting merely of a long series of one 
note, tick, tick, tick, tick, etc., repeated indefinitely. 
Scudder says ensiger begins with a note like brw, then 
pauses an instant and immediately 
emits a rapid succession of sounds 
like chwi at the rate of about five 
per second and continues them an 
unlimited time. McNeil repre- 
sents the notes as zip, zip, zip; 
Davis expresses them as ik, ik, ik; 
and Allard hears them as tsip, tsip, 
tsip. The song of retusus (Fig. 27) 
is quite different. It consists of a 
long shrill whir which Rehn and 
Hebard describe as a continuous 
zeeeeeeeeee. The sound is not loud 
but is in a very high key and rises 
in pitch as the player gains speed 
in his wing movements, till to some 
human ears it becomes almost in- 
audible, though to others it is a 
plain and distinct screech. 

A large conehead and one with 
a much stronger instrument is the 
robust conehead, Neoconocephalus 
robustus (Fig. 28). He is one of 
the loudest singers of North 
American Orthoptera, his song 
being an intense, continuous buzz, 
somewhat resembling that of a 

Cicada. A Caged Specimen Singing fore wings separated and 

in a room makes a deafening noise. somewhat . elevated - the head 

o downward 

The principal buzzing sound is ac- 
companied by a lower, droning hum, the origin of which 
is nor clear, but which is probably some secondary vibra- 
tion of the wings. The player always sits head downward 

Fig. 28. The robust cone- 
head, Neoconocephalus robus- 
tus, in position of singing, with 



while performing, and the breathing motions of the abdo- 
men are very deep and rapid. The robust conehead is an 
inhabitant of dry, sandy places along the Atlantic coast 
from Massachusetts to Virginia and, according to Blatch- 
ley, of similar places near the shores of Lake Michigan in 
Indiana. The writer made its acquaintance in Con- 
necticut on the sandy flats of the Quinnipiac Valley, north 
of New Haven, where its shrill song may be heard on 
summer nights from long distances. 


These are trim, slim little grasshopperlike insects, active 
by day, that live in moist meadows where the vegetation is 
always fresh and juicy. They constitute the subfamily 
Conocephalinae of the katydid family, having conical 

Fig. 29. The common meadow grasshopper, Orchelimum vulgare, a member of 
the katydid family 

heads like the last group, but being mostly of smaller size. 
There are numerous species of the meadow grasshoppers, 
but most of them in the eastern part of the United States 
belong to two genera known as Orchelimum and Conoceph- 
alus. The most abundant and most widely distributed 
member of the first is the common meadow grasshopper, 
Orchelimum vulgare. A male is shown in Figure 19. He 
is a little over an inch in length, with head rather large 
for his size and with big eyes of a bright orange color. The 
ground color of his body is greenish, but the top of the 
head and the thoracic shield is occupied by a long tri- 
angular dark-brown patch, while the stridulating area of 



\ /f/ 


saK , 

ft / // / 


W i 





1 1 



Fig. 30. The hand- 
somt meadow grass- 
hopper, Orchelimum 


Upper figure, a male; 

lower, a female 

lable repeated many times. These two 
elements, the zip and zee, are charac- 
teristic of the songs of all the Orcheli- 
mums, some giving more stress to the 
first and others to the second, and 

the wings is marked by a brown 
spot at each corner. These little 
grasshoppers readily sing in con- 
finement, both in the day and at 
night. Their music is very unpre- 
tentious and might easily be lost 
out of doors, consisting mostly of a 
soft, rustling buzz that lasts two or 
three seconds. Often the buzz is 
preceded or followed by a series of 
clicks made by a slower movement 
of the wings. Frequently the 
player opens the wings for the 
start of the song with a single click, 
then proceeds with the buzz, and 
finally closes with a few slow 
movements that produce the con- 
cluding series of clicks. But very 
commonly he gives only the buzz 
without prelude 
or staccato end- 

Another com- 
mon member of 
the genus is the 
agile meadow 
grasshopper, Or- 
chelimum agile. 
Its music is said 
to be a long zip, 
zip, zip, zee-e-e-e, 
with the zip syl- 

Fig. 31. The slender 
meadow grasshopper, 
Conocephalus fasciatus, 
one of the smallest 
members of the katy- 
did family 



sometimes either one or the other is omitted. A very 
pretty species of the genus is the handsome meadow 
grasshopper, Orchelimum laticauda (or pulchellum) shown 
in Figure 30. When at rest, both males and females 
usually sit close to a stem or leaf with the middle of the 
body in contact with the support and the long hind legs 
stretched out behind. Davis says the song ot this species 
is a zip, zip, zip, z, z, z, qviite distinguishable from that of 
0. vulgare. 

Still smaller meadow grasshoppers belong to the genus 
Conocephalus, more commonly called Xiphidium. One of 
the most abundant species, the slender meadow grass- 
hopper, C. fasciatus, is shown in Figure 31. It is less than 
an inch in length, the body green, the back of the thorax 
dark brown, the wings reddish-brown, and the back of the 
abdomen marked with a broad brown stripe. Allard says 
the song of this little meadow grasshopper may be ex- 
pressed as tip, tip, tip, tseeeeeeeeeeeeee, but that the entire 
song is so faint as almost to escape the hearing. Piers 
describes it as ple-e-e-e-e-e, tzit, tzit, tzit, tzit. Like the song 
of Orchelimum vulgare it apparently may either begin or 
end with staccato notes. 


Another large group of the katydid family is the sub- 
family Decticinae, mostly cricketlike insects that live on 
the ground, but which have wings so short (Fig. 32) that 
they are poor musicians. They are called "shield bearers" 
because the large back plate of the first body segment is 
more or less prolonged like a shield over the back. Most of 
the species live in the western parts of the United States, 
where the individuals sometimes become so abundant as 
to form large and very destructive bands. One such 
species is the Mormon cricket, Anabrus simplex, and an- 
other is the Coulee cricket, Peranabrus scabricollis (Fig. 32), 
of the dry central region of the State of Washington. The 
females of these species are commonly wingless, but the 



males have short stubs of front wings that retain the 
stridulating organs and enable them to sing with a brisk 

Still another large subfamily of the Tettigoniidae is the 

Fig. 32. The Coulee cricket, Peranabrus scabricollis^ male and female, an 
example of a cricketlike member of the katydid family 

Rhadophorinae, including the insects known as "camel 
crickets." But these are all wingless, and therefore silent. 

The Cricket Family 

The chirp of the cricket is probably the most familiar 
note of all orthopteran music. But the only cricket com- 
monly known to the public is the black field cricket, the 
lively chirper of our yards and gardens. His European 
cousin, the house cricket, is famous as the "cricket on the 
hearth" on account of his fondness for fireside warmth 
which so stimulates him that he must express his animation 
in song. This house cricket has been known as Gryllus 
since the time of the ancient Greeks and Romans, and his 
name has been made the basis for the name of his family, 
the Gryllidae, for there are numerous other crickets, some 
that live in trees, some in shrubbery, some on the ground, 
and others in the earth. 

The crickets have long slender antennae like those of the 
katydids, and also stridulating organs on the bases of the 
wings, and ears in their front legs. But they differ from the 
katydids in having only three joints in their feet (Fig. 
17 C). The cricket's foot in this respect resembles the foot 



of the grasshopper (A), but usually differs from that of the 
grasshopper in having the basal joint smooth or hairy all 
around or with only one pad on the under surface. In most 
crickets, also, the second joint of the foot is very small. 

Sc R M 

Sc R M 

Fxc. 33. The wings of a tree cricket 

A, right front wing of an immature female, showing norma! arrangement of 
veins: Sc, subcosta; R, radius; M, media; Cut, first branch of cubitus; Cut, 

second branch of cubitus; lA, first anal. (From Comstock and Needham) 

B, front wing of an adult female of the narrow-winged tree cricket 

C, front wing of an immature male, showing widening of inner half to form 
vibrating area, or tympanum, and modification ot veins in this area. (From 

Comstock and Needham) 

D, right front wing of adult male of the narrow-winged tree cricket; the second 

branch of cubitus {Cut) becomes the curved file vein (h); s, the scraper 

Some crickets have large wings, some small wings, some no 
wings at all. The females are provided with long oviposi- 
tors for placing their eggs in twigs of trees or in the ground 

( Fi g s - 35> 3 6 )- 

The musical or stridulating organs of the crickets are 
similar to those of the katydids, being formed from the 
veins of the basal parts of the front wings. But in the 
crickets the organs are equally developed on each wing, and 
it looks as if these insects could play with either wing up- 
permost. Yet most of them consistently keep the right 



wing on top and use the file of this wing and the scraper 
of the left, just the reverse of the custom among the 

The front wings of male crickets are usually very broad 
and have the outer edges turned down in a wide flap that 
folds over the sides of the body when the wings are closed. 
The wings of the females are simpler and usually smaller. 
The differences between the front wings in the male and 
the female of one of the tree crickets (Fig. 37) is shown 
at B and D of Figure 23- The inner half of the wing (or 
the rear half when the wing is extended) is very large in the 
male (D) and has only a few veins, which brace or stiffen 
the wide membranous vibratory area or tympanum. The 
inner basal part, or anal area, of the male wing is also 
larger than in the female and contains a prominent vein 
{Cu-i) which makes a sharp curve toward the edge of the 
wing. This vein has the stridulating file on its under sur- 
face. The veins in the wing of an 
adult female (B) are comparatively 
simple, and those of a young female (A) 
are more so. But the complicated 
venation of the male wing has been de- 
veloped from the simple type of the 
female, which is that common to in- 
sects in general. The wing of a young 
male (C) is not so different from that 
of a young female (A) but that the cor- 
responding veins can be identified, as 
shown by the lettering. Taking next 
the wing of the adult male (D), it is an 
easy matter to determine which veins 
have been distorted to produce the 
stridulating apparatus. When the tree 
crickets sing they elevate the wings above the back like 
two broad fans (Figs. 37, 40) and move them sidewise so 
that the file of the right rubs over the scraper of the 

Fig. 34. A mole cricket, 
Neocurtilla hexadactyla 




The mole crickets (Fig. 34) are solemn creatures of the 
earth. They live like true moles in burrows underground, 
usually in wet fields or along streams. Their forefeet are 
broad and turned outward for digging like the front feet of 
moles. But the mole crickets differ from real moles in 
having wings, and sometimes they leave their burrows at 
night and fly about, being occasionally attracted to lights. 
Their front wings are short and lie flat on the back over 
the base of the abdomen, but the long hind wings are 
folded lengthwise over the back and project beyond the tip 
of the body. 

Notwithstanding the gloomy nature of their habitat, the 
male mole crickets sing. Their music, however, is solemn 
and monotonous, being always a series of loud, deep-toned 
chirps, like churp, churp, churp, repeated very regularly 
about a hundred times a minute and continued indefinitely 
if the singer is not disturbed. Since the notes are most 
frequently heard coming from a marshy field or from the 
edge of a stream, they might be supposed to be those of a 
small trog. It is difficult to capture a mole cricket in the 
act of singing, tor he is most likely standing at an opening 
in his burrow into which he retreats before he is discovered. 


This group of crickets includes Gryllus as its typical 
member, but entomologists give first place to a smaller 
brown cricket called Nemobius. There are numerous spe- 
cies of this genus, but a widely distributed one is N. vitta- 
tus, the striped ground cricket. This is a little cricket, 
about three-eighths of an inch in length, brownish in color, 
with three darker stripes on the abdomen, common in 
fields and dooryards (Fig. 35). In the fall the females lay 
their eggs in the ground with their slender ovipositors 
(D, E) and the eggs (F) hatch the following summer. 

The song of the male Nemobius is a continuous twitter- 



Fig. 35. The striped ground cricket, Nemobius vittatus 
A, B, females, distinguished by the long ovipositor. C, a male. D, a female 
in the act of thrusting her ovipositor into the ground. E, a female, with oviposi- 
tor full length in the ground, and extruding an egg from its tip. F, an egg in 

the ground 

ing trill so faint that you must listen attentively to hear it. 
In singing the male raises his wings at an angle of about 
45 . The stridulating vein is set with such fine ridges that 



they would seem incapable of producing even those whis- 
pering Nemobius notes. Most of the muscial instruments 
of insects can be made to produce a swish, a creak, or a 
grating noise of some sort when handled with our clumsy 
fingers or with a pair of forceps, but only the skill of the 
living insect can bring from them the tones and the volume 
of sound they are capable of producing. 

Our best-known cricket is Gryllus, the black cricket 
(Fig. 36), so common everywhere in fields and yards and 
occasionally entering houses. The true house cricket of 
Europe, Grvllus domesticus, has become naturalized in this 
country and occurs in small numbers through the Eastern 
States. But our common native species is Gryllus assimilis. 
Entomologists distinguish several varieties, though they 
are inclined to regard them all as belonging to the one 

Mature individuals of Gryllus are particularly abundant 
in the fall; in southern New England they appear every 
year at this season by the millions, swarming everywhere, 
hopping across the country roads in such numbers that it is 
impossible to ride or walk without crushing them. Most 
of the females lay their eggs in September and October, de- 
positing them singly in the ground (Fig. 36 D, E) in the 
same way that Nemobius does. These eggs hatch about 
the first of June the following year. But at this same time 
another group of individuals reaches maturity, a group 
that hatched in midsummer of the preceding year and 
passed the winter in an immature condition. The males of 
these begin singing at Washington during the last part of 
May, in Connecticut the first of June, and may be heard 
until the end of June. Then there is seldom any sound of 
Gryllus until the middle of August, when the males of the 
spring group begin to mature. From now on their notes 
become more and more common and by early fall they are 
to be heard almost continuously day and night until frost. 

The notes of Gryllus are always vivacious, usually cheer- 
ful, sometimes angry in tone. They are merely chirps, and 



may be known from all others by a broken or vibratory 
sound. There is little music in them, but the player has 
enough conceit to make up for this lack. Two vigorous 

Fig. 36. The common black cricket, Qryllus assimilis 

A, a male with wings raised in the attitude of singing. B, a female with long 

ovipositor. C, young crickets recently hatched (enlarged about i'i times). 

D, a female inserting her ovipositor in the ground. E, a female with ovipositor 

buried full length in the ground 



males that were kept in a cage together with several 
females gave each other little peace. Whenever one began 
to play his riddle the other started up, to the plain disgust 
of the first one, and either was always greatly annoyed and 
provoked to anger it any of the females happened to run 
into him while he was playing. If one male was fiddling 
alone and the other approached him, the first dashed at 
the intruder with jaws open, increasing the speed of his 
strokes at the same time till the notes became almost a 
shrill whistle. The other male usually retaliated by play- 
ing, too, in an apparent attempt to outfiddle the first. The 
chirps from both sides now came quicker and quicker, their 
pitch mounting higher and higher, till each player reached 
his limit. Then both would stop and begin over again. 
Neither male ever inflicted any actual damage on his rival, 
and in spite of their savage threats neither was ever seen 
really to grasp any part of the other with his jaws. Either 
would dash madly at a female that happened to disturb 
him while fiddling, but neither was ever seen to threaten a 
female with open jaws. 

The weather has much influence on the spirits of the 
males; their chirps are alwavs loudest and their rivalry 
keenest when it is bright and warm. Setting their cage in 
the sun on cold days always started the two males at once 
to singing. Out of doors, though the crickets sing in all 
weather and at all hours, variations oi their notes in tone 
and strength according to the temperature are very notice- 
able. This is not owing to any effect of humidity on their 
instruments, for the two belligerent males kept in the house 
never had the temper on cold and gloomy days that char- 
acterized their actions and their song on days that were 
warm and bright. This, in connection with the fact that 
their music is usually aimed at each other in a spirit clearly 
suggestive of vindictiveness and anger, is all good evidence 
that Gryllus sings to express himself and not to "charm the 
females." In fact, it is often hard to feel certain whether 
he is singing or swearing. If we could understand the 

I 62 I 


words, we might be shocked at the awful language he is 
hurling at his rival. However, swearing is only a form of 
emotional expression, and singing is another. Gryllus, 
like an opera singer, simplv expresses all his emotions in 
music, and, whether we can understand the words or not, 
we understand the sentiment. 

At last one of the two caged rivals died; whether from 
natural causes or by foul means was never ascertained. 
He was alive early on the day of his demise but apparently 
weak, though still intact. In the middle of the afternoon, 
however, he lay on his back, his hind legs stretched out 
straight and stiff; only a few movements of the front legs 
showed that life was not yet quite extinct. One antenna 
was lacking and the upper lip and adjoining parts of the 
face were gone, evidently chewed off. But this is not neces- 
sarily evidence that death had followed violence, for, in 
cricketdom, violence more commonly follows death; that 
is, cannibalism is substituted for interment. A few days 
before, a dead female in the cage had been devoured 
quickly, all but the skull. After the death of this male, 
the remaining one no longer fiddled so often, nor with the 
same sharp challenging tone as before. Yet this could not 
be attributed to sadness; he had despised his rival and had 
clearly desired to be rid of him; his change was due rather 
to the lack of any special stimulus for expression. 


The unceasing ringing that always rises on summer eve- 
nings as soon as the shadows begin to darken, that shrill 
melody of sound that seems to come from nothing but 
from everywhere out of doors, is mostly the chorus of the 
tree crickets, the blend of notes from innumerable harpists 
playing unseen in the darkness. This sound must be the 
most familiar of all insect sounds, but the musicians them- 
selves are but little known to the general public. And 
when one of them happens to come to the window or into 
the house and plays in solo, the sound is so surprisingly 



loud that the player is not suspected of being one of that 
band whose mingled notes are heard outside softened by 
distance and muffled by screens of foliage. 

Out of doors the music of an individual cricket is so 
elusive that even when you think you have located the ex- 

FiG. 37. The snowy tree cricket, Oecanthus niveus 

The upper figures, males, the one on the right with fore wings 

raised vertically in attitude of singing; below, a female, with 

narrow wings folded close against the body 

act bush or vine from which it comes the notes seem to 
shift and dodge. Surely, you think, the player must be 
under that leaf; but when you approach your ear to it, the 
sound as certainly comes from another over yonder; but 
here you are equally convinced that it comes from still 



another place farther off. Finally, though, it strikes the 
ear with such intensity that there can be no mistaking the 
source of its origin, and, right there in plain sight on a leaf 
sits a little, delicate, slim-legged, pale-green insect with 
hazy, transparent sails outspread above its back. But 
can such an insignificant creature be making such a deafen- 
ing sound! It has required very cautious tactics to ap- 
proach thus close without stopping the music, and it needs 
but a touch on stem or leaf to make it cease. But now 
those gauzy sails that before were a blurred vignette have 
acquired a definite outline, and a little more disturbance 
may cause them to be lowered and spread flat on the 
creature's back. The music will not begin anew until you 
have passed a period of silent waiting. Then, suddenly, 
the lacy films go up, once more their outlines blur, and 
that intense scream again pierces your ear. In short, you 
are witnessing a private performance of the broad-winged 
tree cricket, Oecanthns latipennis. 

But if you pay attention to the notes of other singers, 
you will observe that there is a variety of airs in the medley 
going on. Many notes are long trills like the one just 
identified, lasting indefinitely; but others are softer purr- 
ing sounds, about two seconds in length, while still others 
are short beats repeated regularly a hundred or more times 
every minute. The last are the notes of the snowy tree 
cricket, Oecanthus niveus, so-called on account of his pale- 
ness. He is really green in color, but a green of such a 
very pale shade that he looks almost white in the dark. The 
male (Fig. 37) is a little longer than half an inch, his wings 
are wide and flat, overlapping when folded on the back, 
with the edges turned down against the sides of the body. 
The female is heavier-bodied than the male, but her wings 
are narrow, and when folded are furled along the back. 
She has a long ovipositor for inserting her eggs into the 
bark of trees. 

The males of the snowy cricket reach maturity and begin 
to sing about the middle of July. The singer raises his 



wings vertically above the back and vibrates them sidewise 
so rapidly that they are momentarily blurred with each 
note. The sound is that treat, treat, treat, treat already de- 
scribed, repeated regularly, rhythmically, and monoto- 
nously all through the night. At the first of the season 
there may be about 125 beats every minute, but later, on 
hot nights, the strokes become more rapid and mount to 
160 a minute. In the fall again the rate decreases on cool 
evenings to perhaps a hundred. And finally, at the end of 
the season, when the players are benumbed with cold, the 

Fig. 38. Distinguishing marks on the basal segments of the 

antennae of common species of tree crickets 

A, B, narrow-winged tree cricket, Oecanthus angustipennis. C • 

snowy tree cricket, nivcus. D, four-spotted tree cricket, nigri' 

cornis quadripunctatus. E, black-horned tree cricket, nigricornis- 

F, broad-winged tree cricket, latipennis 

notes become hoarse bleats repeated slowly and irregularly 
as if produced with pain and difficulty. 

The several species of tree crickets belonging to the 
genus Oecanthus are similar in appearance, though the 
males differ somewhat in the width of the wings and some 
species are more or less diffused with a brownish color. 
But on their antennae most species bear distinctive marks 
(Fig. 38) by which they may be easily identified. The 
snowy cricket, for example, has a single oval spot of black 
on the under side of each of the two basal antennal joints 
(Fig. 38 C). Another, the narrow-winged tree cricket, has 



a spot on the second joint and a black J on the first (A, B). 
A third, the four-spotted cricket (D), has a dash and dot 
side by side on each joint. A fourth, the black-horned or 
striped tree cricket (E), has two spots on each joint more 
or less run together, or sometimes has the whole base of 
the antenna blackish, while the color may also spread over 
the fore parts of the body and, on some individuals, form 

Fig. 39. Male and female of the narrow-winged tree cricket, Oecanthus angusti- 

The female is feeding on a liquid exuded from the back of the male, while the 
latter holds his fore wings in the attitude of singing. (Enlarged about 3 times) 

stripes along the back. A fifth species, the broad-winged 
(F), has no marks on the antennae, which are uniformly 

The narrow-winged tree cricket {Oecanthus angusti- 
pennis) is almost everywhere associated with the snowy, 
but its notes are very easily distinguished. They consist 
of slower, purring sounds, usually prolonged about two 
seconds, and separated by intervals of the same length, but 
as fall approaches they become slower and longer. Always 
they are sad in tone and sound far off. 

The three other common tree crickets, the black-horned 
or striped cricket, Oecanthus nigricornis, the four-spotted, 



0. nigricornis quadripunctatus, 
and the broad-winged, 0. lati- 
pennis, are all trillers; that is, 
their music consists of a long, 
shrill whir kept up indefinitely. 
Of these the broad-winged cricket 
makes the loudest sound and the 
one predominant near Washing- 
ton. The black-horned is the 
common triller farther north, and 
is particularly a daylight singer. 
In Connecticut his shrill note 
rings everywhere along the road- 
sides, on warm bright afternoons 
of September and October, as the 
player sits on leaf or twig fully 
exposed to the sun. At this 
season also, both the snowy and 
the narrow-winged sing by day 
but usually later in the after- 
noon and generally from more concealed places. 

We should naturally like to know why these little 
creatures are such persistent 
singers and of what use their 
music is to them. Do the males 
really sing to charm and attract 
the females as is usually pre- 
sumed? We do not know; but 
sometimes when a male is sing- 
ing, a female approaches him 
from behind, noses about on his 
back, and soon finds there a deep 
basinlike cavity situated just 
behind the bases of the elevated 
wings. This basin contains a 
clear liquid which the female 
proceeds to lap up very eagerly, 


Fig. 40. A male of the broad- 
winged tree cricket, Oecanthus 
latipenniS) with wings elevated 
in position of singing, seen from 
above and behind, showing 
the basin (B) on his back into 
which the liquid is exuded that 
attracts the female 

Fig. 41. The back of the 
third thoracic segment of the 
broad-winged tree cricket, 
with its basin (B) that receives 
secretion from the glands (G/) 
inside the body 


as the male remains quiet with wings upraised though he 
has ceased to play (Fig. 39). We must suspect, then, that 
in this case the female has been attracted to the male 
rather by his confectionery offering than by his music. 
The purpose of the latter, therefore, would appear to be to 
advertise to the female the whereabouts of the male, who 
she knows has sweets to offer; or if the liquid is sour or 
bitter it is all the same — the female likes it and comes 
after it. If, now, this luring of the female sometimes ends 
in marriage, we may see here the real reason for the male's 
possessing his music-making organs and his instinct to 
play them so continuously. 

A male cricket with his front wings raised, seen from 
above and behind as he might look to a female, is shown in 
Figure 40. The basin (B) on his back is a deep cavity on 
the dorsal plate of the third thoracic segment. A pair of 
large branching glands (Fig. 41, Gl) within the body open 
just inside the rear lip of the basin, and these glands fur- 
nish the liquid that the female obtains. 

There is another kind of tree cricket belonging to an- 
other genus, Neoxabia, called the two-spotted tree cricket, 
N. bipmictata, on account of two pairs of dark spots on the 
wings of the female. This cricket is larger than any of the 
species of Oecanthus and is of a pinkish brown color. It is 
widely distributed over the eastern half of the United 
States, but is comparatively rare and seldom met with. 
Allard says its notes are low, deep, mellow trills con- 
tinued tor a few seconds and separated by short intervals, 
as are the notes of the narrow-winged Oecanthus, but that 
their tone more resembles that of the broad-winged. 


The bush crickets differ from the other crickets in having 
the middle joint in the foot larger and shaped more like the 
third joint in the foot of a katydid (Fig. 17 B). Among the 
bush crickets there is one notable singer common in the 
neighborhood of Washington. This is the jumping bush 



cricket, Orocharis saltator (Fig. 42), who comes on the stage 
late in the season, about the middle of August, or shortly 
after. His notes are loud, clear, piping chirps with a rising 
inflection toward the end, suggestive of the notes of a 
small tree toad, and they at once strike the listener as 

something new and 

different in the insect 
program. The play- 
ers, however, are at 
first very hard to lo- 
cate, for they do not 
perform continuously 
— one note seems to 
come from here, a 
second from over 
there, and a third 
from a different an- 
gle, so that it is al- 
most impossible to 
place any one of 
them. But after a 
week or so the crick- 
ets become more nu- 
merous and each 

Fig. 42. The Jumping bush cricket, Orocharis 

Upper figure, a male; lower, a female 

player more persistent till soon their notes are the predomi- 
nant sounds in the nightly concerts, standing out loud and 
clear against the whole tree-cricket chorus. As Riley says, 
this chirp "is so distinctive that when once studied it is 
never lost amid the louder racket of the katydids and 
other night choristers." 

After the first of September it is not hard to locate one of 
the performers, and when discovered with a flashlight, he is 
found to be a medium-sized, brown, short-legged cricket, 
built somewhat on the style of Gryllus but smaller (Fig. 
42). The male, however, while singing raises his wings 
straight up, after the manner of the tree crickets, and he 
too, carries a basin of liquid on his back much sought after 



by the female. In fact the liquid is so attractive to her 
that, at least in a cage, she is sometimes so persistent in her 
efforts to obtain it that the male is clearly annoyed and 
tries to avoid her. One male was observed to say very 
distinctly by his actions, as he repeatedly tried to escape 
the nibbling of a female, presumably his wife since she was 
taken with him when captured, "I do wish you would quit 
pestering me and let me sing!" Here is another piece of 
evidence suggesting that the male cricket sings to express 
his own emotions, whatever they may be, and not pri- 
marily to attract the female. But if, as in the case of the 
tree crickets, his music 
tells the female where 
she may find her favorite 
confection, and this in 
turn leads to matrimony, 
when the male is in the 
proper mood, it suggests 
a practical use and a rea- 
son for the stridulating 
apparatus and the song 
of the male insect. 

Walking-Sticks and 
Leaf Insects 

Talent often seems to 
run in families, or in re- 
lated families, but it does 
not necessarily express it- 
self in the same way. If 
the katydids and crickets 
are noted musicians, 
some of their relatives, 
belonging to the family 
Phasmidae, are incomparable mimics. Their mimicry, 
however, is not a conscious imitation, but is one bred in 
their bodily forms through a long line of ancestors. 


Fig. 43. The common walking-stick in- 
sect, Diapheromera femorata t of the eastern 
part of the United States. (Length i]/ 2 


If sometime in the woods you should chance to see a 
short, slender piece of twig suddenly come to life and 
slowly walk away on six slim legs, the marvel would not be 

a miracle, but a walking-stick in- 
sect (Fig. 43). These insects are 
fairly common in the eastern parts 
of the United States, but on ac- 
count of their resemblance to 
twigs, and their habit of remaining 
perfectly quiet tor a long time 
with the body pressed close to a 
branch of a tree, they are more 
frequently overlooked than seen. 
Sometimes, however, they occur 
locally in great numbers. It is 
supposed that the stick insects so 
closely resemble twigs for the pur- 
pose of protection from their 
enemies, but it has not been shown 
just what enemies they avoid by 
their elusive shape. The stick in- 
sects are more common in the 
South and in tropical countries, 
where some attain a remarkable 
length, one species from Africa, 
for example, being eleven inches 
long when full-grown. In New 
Guinea there lives a species that 
looks more like a small club than 
a stick, it being a large, heavy- 
bodied, spiny creature, nearly 
six inches in length and an 
inch in width through the thick- 
est part of its body (Fig. 44). 

Other members of the phasmid family have specialized 
on imitating leaves. These insects have wings in the 
adult stage, and, of course, the wings make it easier for 


Fig. 44. A gigantic spiny 
walking-stick insect, Eury- 
canthus horrida, from New 
Guinea. (Length $*4 


them to take the form of leaves. One famous species that 
lives in the East Indies looks so much like two leaves stuck 
together that it is truly marvelous that an insect could be 
so fashioned (Fig. 45). The 
whole body is flat, and about 
three inches long, the bases of 
the legs are broad and irregu- 
larly notched, the abdomen is 
spread out almost as thin as a 
real leaf, and the leaflike wings 
are held close above it. Finally, 
the color, which is leaf-green 
or brown, gives the last touch 
necessary for complete dissim- 

The Mantids 

It is often observed that 
genius may be perverted, or 
put to evil purposes. Here is a 

r __•! c ■ .1 iv n Fig. 45. A tropical leaf insect, 

family of insects, the Man- PuUhriphylUum pukhriMium, a 

tidae, related tO the graSS- member of the walking-stick fam- 

1 1 j- j 1 • 1 ily- (Length 3 inches) 

hoppers, katydids, and crick- 
ets, the members of which are clever enough, but are 
deceitful and malicious. 

The praying mantis, Stagmomantis Carolina (Fig. 46), 
though he may go by the aliases of "rear-horse" and 
"soothsayer," gets his more common name from the 
prayerful attitude he commonly assumes when at rest. 
The long, necklike prothorax, supporting the small head, 
is elevated and the front legs are meekly folded. But if 
you examine closely one of these folded legs, you will see 
that the second and third parts are armed with suspicious- 
looking spikes, which are concealed when the two parts 
are closed upon each other. In truth, the mantis is an 
arch hypocrite, and his devotional attitude and meek 
looks betoken no humility of spirit. The spiny arms, 



so innocently folded upon the breast, are direful weapons 
held ready to strike as soon as some unsuspecting insect 
happens within their reach. Let a small grasshopper 
come near the posing saint: immediately a sly tilt of the 
head belies the suppliant manner, the crafty eyes leer 
upon the approaching insect, losing no detail of his 
movements. Then, suddenly, without warning, the pray- 
ing mantis becomes a demon in action. With a nice cal- 
culation ot distance, a swift movement, a snatch of the 

Fig. 46. The praying mantis, Stagmomantis Carolina, and remains of its 
last meal. (Length ^} 2 inches) 

terrible clasps, the unlucky grasshopper is a doomed 
captive, as securely held as if a steel trap had closed upon 
his body. As the hapless creature kicks and wrestles, the 
jaws of the captor sink into the back of his head, evidently 
in search of the brain; and hardly do his weakening strug- 
gles cease before the victim is devoured. Legs, wings, 
and other fragments unsuitable to the taste of an epicure 
are thrown aside, when once more the mantis sinks into 
repose, piously folds his arms, and meekly awaits the 



chance arrival of the next 
course in his ever unfinished 
banquet of living fare. 

Some exotic species of 
mantids have the sides of 
the prothorax extended to 
form a wide shield (Fig. 47), 
beneath which the forelegs 
are folded and completely 
hidden. It is not clear what 
advantage they derive from 
this device, but it seems to 
be one more expression of 

Of course, as we shall 
take occasion to observe 
later, goodness and bad- 
ness are largely matters of 

Fig. 47. A mantis from Ecuador with 

a shieldlike extension of its back. 

(Length y/i inches) 

Fig. 48. Egg case of a 

mantis attached to a 

twig, Stagmomantis 


The mantis is an evil creature from the 
standpoint of a grasshopper, but he 
would be regarded as a benefactor by 
those who have a grudge against grass- 
hoppers or against other insects that the 
mantis destroys. Hence, we must reckon 
the mantis as at least a beneficial insect 
relative to human welfare. A large 
species of mantis, introduced a few years 
ago into the eastern States from China, 
is now regarded as a valuable agricul- 
tural asset because of the number of 
harmful insects it destroys. 

The mantids lay their eggs in large 
cases stuck to the twigs of trees (Fig. 48). 
The substance of which the case is made 
is similar to that with which the locusts 
inclose their eggs, and is exuded from the 



body of the female mantis when the eggs are laid. The 
young mantids are active little creatures, without wings 
but with long legs, and it is the fate of those unprotected 
green bugs, the aphids, or plant lice, that infest the leaves 
of almost all kinds of plants, to become the principal 
victims of their youthful appetites. 



We used to speak quite confidently of time as something 
definite, measurable by the clock, and ot a year or a cen- 
tury as specific quantities of duration. In this present age 
ot relativity, however, we do not feel so certain about these 
things. Geologists calculate in years the probable age of 
the earth, and the length of time that has elapsed since 
certain events took place upon it, but their figures mean 
only that the earth has gone around the sun approximately 
so many times during the interval. ! In biology it signifies 
nothing that one animal has been on the earth for a million 
years, and another for a hundred million, for the unit of 
evolution is not a year, but a generation. If one animal, 
such as most insects, has from one to many generations 
every year, and another, such as man, has only four or five 
in a century, it is evident that the first, by evolutionary 
reckoning, will be vastly older than the second, even 
though the two have made the same number of trips with 
the earth around the sun. An insect that antedates man 
by several hundred million years, therefore, is ancient 

The roach scarcely needs an introduction, being quite 
well known to all classes of society in every inhabited part 
of the world. That he has long been established in human 
communities is shown by the fact that the various nations 
have bestowed different names upon him. His common 
English name ot "cockroach" is said to come from the 
Spanish, cucaracha. The Germans call him, rather dis- 
respectfully, kuchenschabe, which signifies "kitchen 

[77 1 


louse/' The ancient Romans called him Blatta, and on 
this his scientific family name of Blattidae is based. A 
small species ot Fairope, named by the entomologists 

Fig. 49. The four species of common household roaches 

A, the German roach, or Croton bug, Blattelia germanica (length % inch). B, 

the American cockroach, Periplaneta arnericana (length i3g inches). C, the 

Australian cockroach, Periplaneta australasiae (length 1% inches). D, the 

wingless female of the Oriental roach, Biatta orientalis (length i>8 inches). E, 
the winged male of the Oriental roach (length 1 inch) 



Blattella germanica, which is now our most common 
American roach, received the nickname of "Croton bug" 
in New York, because somehow he seemed to spread with 
the introduction of the Croton Valley water system, and 
this appelation has stuck to him in many parts of the 

The Croton bug, or German roach (Fig. 49 A), is the 
smallest of the "domestic" varieties of roaches. It is 
that rather slender, pale-brown species, about five-eighths 
of an inch in length, with the two dark spots on the front 
shield of its body. This roach is the principal pest of the 
kitchen in the eastern part of the United States, and prob- 

m 1 mJTfTfVi 



D E 

Fig. 50. Egg cases of five species of roaches. (Twice natural size) 

A, egg case of the Australian roach (fig. 49 C). B, that of the American 

roach (fig. 49 B); the other three are made by out-of-door species 

ably the best support of the trade in roach powders. Sev- 
eral other larger species are fortunately less numerous, 
but still familiar enough. Among these are one called 
the American roach (Fig. 49 B), a second known as the 
Australian roach (C), and a third as the Oriental roach 
(D, E). These four species of cockroaches are all great 
travelers and recognize no ties of nationality. They are 
equally at home on land and at sea, and, as uninvited 



passengers on ships, they have spread to all countries 
where ships have gone. 

Besides the household roaches, there are great numbers 
of species that live out of doors, especially in warm and 
tropical regions. Most of these are plain brown of various 
shades, or blackish, but some are green, and a few are 
spotted, banded, or striped. Different species vary much 
in size, some of the largest reaching a length of four inches, 
measured to the tips of the folded wings, while the smallest 
are no longer than three thirty-seconds of an inch in 
length. They nearly all have the familiar flattened form, 
with the head bent down beneath the front part of the 
body, and the long, slender antennae projecting forward. 
Most species have wings which they keep closely folded 
over the back. In the Oriental roach, the wings of the 
female are very short (Fig. 49 D), a character which gives 
them such a different appearance from the males (E) that 
the two sexes were formerly supposed to be differen t species. 

The roach, of course, was not designed to be a household 
insect, and it lived out of doors for ages before man con- 
structed dwellings, but it happens that its instincts and its 
form of body particularly adapt it to a life in houses. Its 
keen sense, its agility, its nocturnal habits, its omnivorous 
appetite, and its flattened shape are all qualities very 
fitting for success as a domestic pest. 

Many kinds of roaches give birth to living young; but 
most of our common species lay eggs, which they inclose in 
hard-shelled capsules. The material of the capsule is a 
tough but flexible substance resembling horn, and is pro- 
duced as a secretion by a special gland in the body of the 
female opening into the egg duct. The capsule is formed 
in the egg duct, and the eggs are discharged into it while 
the case is held in the orifice of the duct. When the re- 
ceptacle is full its open edge is closed, and the eggs are thus 
tightly sealed within it. The sealed border is finely 
notched, and transverse impressions on the surface of the 
capsule indicate the position of the eggs within it. 



The Croton bug, or German roach (Fig. 49 A), makes a 
small flat tabloid egg case, which the female usually carries 
about with her for some time projecting from the end of 
her body, and sometimes the eggs hatch while she is still 
carrying the case. The American and Australian roaches 
(Fig. 49 B, C) make egg cases much resembling miniature 
pocketbooks or tobacco pouches, about three-eighths or 
half an inch in length, with a serrated clasp along the upper 
edge (Fig. 50 A, B). The cases of some of the smaller 
species of roaches are only one-sixteenth of an inch long 

Fig. 51. Young of the German roach, or Croton bug (fig. 49 A), in various 

stages just before and after hatching 
A, the young roach in the egg iust before hatching. B, the young roach just 
after hatching, shedding its embryonic covering membrane. C, young roach 
after shedding the embryonic covering. D, the same individual half an hour old 

(C), while larger species may make a case three-quarters 
of an inch in length (E). 

The embryo roaches mature within the eggs, and when 
they are ready to hatch they emerge inside the egg case. 
By some means, the roughened edge of the case where it 
was last closed is opened to allow the imprisoned insects 
to escape. Small masses of the tiny creatures now bulge 
out, and finally the whole wriggling contents of the cap- 
sule is projecting from the slit. First one or two indi- 
viduals free themselves, then several together fall out, 
then more of them, until soon the case containing the 
empty eggshells is deserted. 



When the young roaches first liberate themselves from 
the capsule, they are helpless creatures, for each is con- 
tained in a close-fitting membrane that binds its folded 
legs and antennae tightly to the body and keeps the head 
pressed down against the breast (Fig. 51 A). The inclos- 
ing sheath, however, a film so delicate as to be almost 
invisible, is soon burst by the struggling of the little roach 
anxious to be free — it splits and rapidly slides down over 
the body (B), from which it is at last pushed off. The 
shrunken, discarded remnant of the skin is now such an 
insignificant flake that it scarce seems possible it so re- 
cently could have enveloped the body of the insect. 

The newly liberated young roach dashes off on its slim 
legs with an activity quite surprising in a creature that has 
never had the use of its legs before. It is so slender of 
figure (Fig. 51 C) that it does not look like a roach, and it is 
pale and colorless except for a mass of bright green material 
in its abdomen. But, almost at once, it begins to change; 
the back plates of the thorax flatten out, the body shortens 
by the overlapping of its segments, the abdomen takes on 
a broad, pear-shaped outline, the head is retracted be- 
neath the prothoracic shield, and by the end of half an 
hour the little insect is unmistakably a young cockroach 

The roaches have a potent enemy in the house centipede, 
that creature of so many legs (Fig. 52) that it looks like 
an animated blur as it occasionally darts across the living- 
room floor or disappears in the shades of the basement 
before you are sure whether you have seen something or 
not, but which is often trapped in the bathtub, where its 
appearance is likely to drive the housewife into hysteria. 
Unless you are fond of roaches, however, the house centi- 
pede should be protected and encouraged. The writer 
once placed one of these centipedes in a covered glass dish 
containing a female Croton bug and a capsule of her eggs 
which were hatching. No sooner were the young roaches 
running about than the centipede began a feast which 



ended only when the last of the brood had been devoured. 
The mother roach was not at the time molested, but next 
morning she lay dead on her back, her head severed and 
dragged some distance from the 
body, which was sucked dry of 
its juices — mute evidence of the 
tragedy that had befallen some- 
time in the night, probably when 
the pangs of returning hunger 
stirred the centipede to renewed 
activity. The house centipede 
does not confine itself to a diet of 
live roaches, for it will eat almost 
any kind of food, but it is never 
a pest of the household larder. 

Most species of roaches have 
two pairs of well-developed 
wings, which they ordinarily keep 
folded over the back, for in their 
usual pursuits the domestic spe- 
cies do not often fly, except oc- 
casionally when hard pressed to 
avoid capture. The front wings 
are longer and thicker than the 
hind wings, and are laid over the 
latter, which are thin and folded 
fanwise when not in use. In these 
characters the roaches resemble 
the grasshoppers and katydids, 
and their family, the Blattidae, is 
usually placed with these insects in the order Orthoptera. 

The wings of insects are interesting objects to study. 
When spread out flat, as are those of the roach shown in 
Figure 53, they are seen to consist of a thin membranous 
tissue strengthened by many branching ribs, or veins, 
extending outward from the base. The wings of all insects 
are constructed on the same general plan and have the 


Fig. 52. The common house 

centipede, Sctttigera forceps 

{natural size), a destroyer of 

young roaches 


same primary veins; but, since the great specialty of in- 
sects is flight, in their evolution they have concentrated 
on the wings, and the different groups have tried out 
different stvles of venation, with the result that now 
each is distinguished by some particular pattern in the 
arrangement of the veins and their branches. The 
entomologist can thus not only distinguish by their wing 
structure the various orders of insects, as the Orthoptera, 
the dragonflies, the moths, the bees, and the flies, but in 

Kic. 5"). Wings of a cockroach, Periplamla, showing the vein 
pattern characteristic of the roach family 

many cases he can identify families and even genera. 
Particularly are the wings of value to the student of fossil 
insects, for the bodies are so poorly preserved in most 
cases that without the wings the paleontologist could 
have made little headway in the study of insects of the 
past. As it is, however, much is known of insects of 
former times, and a study of their fossil remains has con- 
tributed a great deal to our knowledge of this most 
versatile and widespread group of animals. 



The paleontological history of life on the earth shows 
us that the land has been inhabited successively by 
different forms of animals and plants. A particular group 
of creatures appears upon the scene, first in comparative 
insignificance; then it increases in numbers, in diversity 
of forms, and usually in the size of individuals, and may 
become the dominant form of life; then again it falls 
back to insignificance as its individuals decrease in size, 
its species in numbers, until perhaps its type becomes 
extinct. Meanwhile another group, representing another 
type of structure, comes into prominence, flourishes, and 
declines. It is a mistake, however, to get the impression 
that all forms of life have had this succession of up and 
down in their history, for there are many animals that 
have existed with little change for immense periods of 

The history of insects gives us a good example of per- 
manence. The insects must have begun to be insects 
somewhere in those remote periods of time before the 
earliest known records of animals were preserved in the 
rocks. They must have been present during the age when 
the water swarmed with sharks and great armored fishes; 
they certainly flourished during the era when our coal 
beds were being deposited; they saw the rise of the huge 
amphibians and the great reptilian beasts, the Dinosaurus, 
the Ichthyosaurus, the Plesiosaurus, the Mosasaurus, and 
all the rest of that monster tribe whose names are now 
familiar household words and whose bones are to be seen 
in all our museums. The insects were branching out 
into new forms during the time when birds had teeth and 
were being evolved from their reptile ancestors, and when 
the flowering plants were beginning to decorate the land- 
scape; they were present from the beginning of the age 
of mammals to its culmination in the great fur-bearing 
creatures but recently extinct; they attended the advent 
of man and have followed man's whole evolution to the 
present time; they are with us yet — a vigorous race that 



shows no sign of weakening or of decrease in numbers. 
Of all the land animals, the insects are the true blue-blood 
aristocrats by length of pedigree. 

The first remains of insects known are found in the 
upper beds of the rocks laid down in the geological period 
of the earth's history known as the Carboniferous. Dur- 

Fig. 54. A group of common Carboniferous plants reaching the size and pro- 
portions of large trees. (From Chamberlin and Salisbury, drawn by Mildred 
Marvin from restorations of fossil specimens.) Courtesy of Henry Holt & Co. 
Of the two large trees in the foreground, the one on the left is a Sigillaria, that 
on the right a Lepidodendron; of the two large central trees in the background 
the left :3 a Cordaite's, the right a tree fern; the tall stalks in the outermost circle 
are Calamites, plants related to our horsetail ferns 

ing Carboniferous times much of the land along the 
shores of inland seas or lakes was marshy and supported 
great forests from which our coal deposits have been 
formed. But the Carboniferous landscape would have 
had a strange and curious look to us, accustomed as we 

[86 1 


are to an abundance of hard-wood, leafy trees and shrubs, 
and a multitude of flowering plants. None of these 
forms of vegetation had yet appeared. 

Much of the undergrowth of the Carboniferous swamps 
was composed of fernlike plants, many of which were, 
indeed, true ferns, and perhaps the ancestors of our 
modern brackens. Some of these ancient ferns grew to 
a great size, and rose above the rest in treelike forms, at- 
taining a height of sixty feet and more, to branch out 
in a feathery crown of huge spreading fronds. Another 
group of plants characteristic of the Carboniferous flora 
comprised the seed ferns, so named because, while closely 
resembling ferns in general appearance, they differed 
from true ferns in that they bore seeds instead of spores. 
The seed ferns were mostly small plants with delicate, 
ornate leaves, and they have left no descendants to modern 

Along with the numerous ferns and seed ferns in the 
Carboniferous swamps, there were gigantic club mosses, 
or lycopods, which, ascending to a height sometimes of 
much more than a hundred feet, were the conspicuous big 
trees in the forests of their day (Fig. 54). These lycopods 
had long, cylindrical trunks covered with small scales 
arranged in regular spiral rows. Some had thick branch- 
ing limbs starting from the upper part of the trunk and 
closely beset with stiff, sharp-pointed leaves; others 
bore at the top of the trunk a great cluster of long slender 
leaves, giving them somewhat the aspect of a gigantic 
variety of our present-day yucca, or Spanish bayonet. 
The bases of the larger trees expanded to a diameter of 
three or four feet, and were supported on huge spreading 
underground branches from which issued the roots — a 
device, perhaps, that gave them an ample foundation in 
the soft mud of the swamps in which they grew. 

The Carboniferous lycopods furnished most of our coal, 
and then, in later times, their places were taken by other 
types of vegetation. But their race is not yet extinct, 



for we have numerous representatives of them with us 
today in those lowly evergreen plants known as club 
mosses, whose spreading, much-branched limbs, usually 
trailing on the ground, are covered by rows of short, 
stiff leaves. The most familiar of the club mosses, though 
not a typical species, is the "ground pine." This humble 
little shrub, so much sought for Christmas decoration, 
still in some places carpets our woods with its soft, broad, 
frondlike stems. In the fall when its rich dark green 
so pleasingly contrasts with the somber tones of the 
season's dying foliage, it seems to be an expression of 
the vitality that has preserved the lycopod race through 
the millions of years which have elapsed since the days of 
its great ancestors. The "resurrection plant," often sold 
to housekeepers under false or exaggerated claims of a 
marvelous capacity for rejuvenation, is also a descendant 
of the proud lycopods of ancient times. 

In our present woodlands, along the banks of streams 
or in other moist places, there grows also another plant 
that has been preserved to us from the Carboniferous 
forests — the common "horsetail fern," or Equisetum, that 
green, rough-ribbed stalk with the whorls of slender 
branches growing from its joints. Our equisetums are 
modest plants, seldom attaining a height of more than a 
few feet, though in South American countries some species 
may reach an altitude of thirty feet; but in Carboniferous 
times their ancestors grew to the stature of trees (Fig. 54) 
and measured their robust stalks with the trunks of the 
lycopods and giant ferns. 

Aside from the numerous representatives of these sev- 
eral groups of plants, all more or less allied to the ferns, 
the Carboniferous forests contained another group of 
treelike plants, called Cordaites, from which the cycads 
of later times and our present-day maidenhair tree, or 
ginko, are probably descended. Then, too, there were a 
few representatives of a type that gave origin to our 
modern conifers. 



It is probable that a visitor to those days of long ago 
might give us a more complete account of the vegetation 
that grew in the Carboniferous swamps than can be known 
from the records of the rocks, but the paleobotanist has 
a wealth of material now at hand sufficient to give us 
at least a pretty reliable picture of the setting in which 
the earliest of known insects lived and died. 

And now, what were the insects like that inhabited 
the forests of those early times? Were they, too, strangely 
fashioned creatures, fit denizens of a far-off fairyland? 
No, nothing of the sort, at least not in appearance or 
structure, though "fit" they probably were, from a physi- 
cal standpoint, for insects are fitted to live almost any- 
where. In short, the Carboniferous insects were prin- 
cipally roaches! Yes, those woods and swamps of millions 
of years ago were alive with roaches little different from 
our own familiar household pests, or from the numerous 
species that have not forsaken their native habitats for 
life in the cities. 

Whoever looks to the geological records for evidence 
of the evolution of insects is sorely disappointed, for 
even in the venation of the wings those early roaches 
(Fig. 55) were almost identical with our present species 
(Fig. 53). As typical examples of the Carboniferous 
roaches, the species shown in Figure 55 serve well, and 
anyone can see, even though the specimens lack antennae 
and legs, that the creatures were just common roaches. 
Hence, we can easily picture these ancient roaches scut- 
tling up the tall trunks of the scaly lycopbds, and shuffling 
in and out among the bases ot the close-set leaf stems 
of the tree ferns, and we should expect to find an abundant 
infestation of them in the vegetational refuse matted on 
the ground. Insects of those days must have been com- 
paratively free from enemies, for birds did not yet exist, 
and all that host of parasitic insects that attack other 
insects were not evolved until more recent times. 

Though by far the greater number of the Carboniferous 



insects known are roaches, or insects closely related to 
roaches, there were many other forms besides. Some of 
these are of particular interest to entomologists because, 
in some ways, they are more simple in structure than are 


Fig. 5 c. Fossil cockroaches from Upper Carboniferous rocks 

A, A ' semoblatta mazorta, found in Illinois, length of wing one inch. 

(From Handlirsch after Scudder.) B, Phyloblalta carbonaria, 

found in Germany. (From Handlirsch) 

any of the modern insects, and in this respect they ap- 
parently stand closer to the hypothetical primitive insects 
than do any others that we know. And yet, the charac- 
ters by which these oldest known insects, called the 
Paleodictvoptera, differ from modern forms are so slight 
that they would scarcely be noticed by anyone except 
an entomologist; to the casual observer, the Paleodic- 
tyoptera would be just insects. Their chief distinguish- 
ing marks are in the pattern of the wing venation, which 
is more symmetrical than in other winged insects, and, 
therefore, probably closer to that of the primitive ances- 
tors of all the winged insects. These ancient insects 
probably did not fold the wings over the back, as do most 
present-day insects, showing thus another primitive 



character, though not a distinctive one, since modern 
dragonflies (Fig. 58) and mayflies (Fig. 60) likewise 
keep the wings extended when at rest. 

The question of how insects acquired wings is always 
one ot special interest, since, while we know perfectly 
well that the wing of a bird or of a bat is merely a modi- 
fied fore limb, the nature of the primitive organ from 
which the insect wing has been evolved is still a mystery. 
The Paleodictyoptera, however, may throw light upon 
the subject, for some of them had small flat lobes on the 
lateral edges of the back plate of the prothorax, which in 
fossil specimens look like undeveloped wings (Fig. 56). 
The presence of these prothoracic lobes, occurring as they 
do in some of the oldest known insects, has suggested the 

Fig. 56. Examples of the earliest known fossil insects, called the Paleodic- 
tyoptera, having small lobes (a) projecting like wings from the prothorax 
A, Slenodictya lobata (from Brongniart). B, Eubleptus daniehi (drawn from 
specimen in U. S. Nat. Mus.): Ti, 72, 7j, back plates of three thoracic segments 

idea that the true wings were evolved from similar flaps 
of the mesothorax and metathorax. If so, we must pic- 
ture the immediate ancestors of the winged insects as 
creatures provided with a row of three flaps on each side 
of the body projecting stiffly outward from the edges of 
the thoracic segments. Of course, the creatures could 
not actually fly with wings of this sort, but probably 



they could glide through the air from the branches of one 
tree to another as well as can a modern flying squirrel by 
means of the folds of skin stretched along the sides of its 
body between the fore and the hind legs. If such lobes 
then became flexible at their bases, it required only a 
slight adjustment of the muscles already present in the 
body to give them motion in an up-and-down direction; 
and the wings of modern insects, in most cases, are still 
moved by a very simple mechanism which has involved 
the acquisition of few extra muscles. 

It appears, however, that three pairs of fully-developed 
wings would be too many for mechanical efficiency. In 
the later evolution of insects, therefore, the prothoracic 
lobes were never developed beyond the glider stage, and 
in all modern insects this first pair of lobes has been lost. 
Furthermore, it was subsequently found that swift flight 
is best attained with a single pair of wings; and nearly 
all the more perfected insects of the present time have 
the hind pair of wings reduced in size and locked to the 
front pair to insure unity of action. The flies have 
carried this evolution toward a two-winged condition so 
far that they have practically achieved the goal, for with 
them the hind wings are so greatly reduced that they 
no longer have the form or function of organs of flight, and 
these insects, named the Diptera, or two-winged insects, 
fly with one highly specialized and efficient pair of wings 
(Fig. 167). 

The Paleodictyoptera became extinct by the end of the 
Carboniferous period, and their disappearance gives 
added support to the idea that they were the last sur- 
vivors of an earlier type of insect. But they were by 
no means the primitive ancestors of insects, for, in the 
possession of wings alone, they show that they must have 
undergone a long evolution while wings were in the course 
of development; but of this stage in the history of insects 
we know nothing. The rocks, so far as has yet been 
revealed, contain no records of insect life below the upper 



beds of the Carboniferous deposits, when insects were 
already fully winged. This fact shows how cautious 
we must be in making negative statements concerning 
the extinct inhabitants of the earth, for we know that 
insects must have lived long before we have evidence of 
their existence. The absence of insect fossils earlier than 
the Carboniferous is hard to explain, because for millions 
of years the remains of other animals and plants had 

Fig. 57. Machilis, a modern representative of ancient insects before the 
development of wings. (Length of body . 5 ie inch) 

been preserved, and have since been found in compara- 
tive abundance. As a consequence, we have no concrete 
knowledge of insects before they became winged creatures 
evolved almost to their modern form. 

At the present time there are wingless insects. Some 
of them show clearlv that thev are recent descendants 
from winged forms. Others suggest bv their structure 
that their ancestors never had wings. Such as these, 
therefore, may have come down to us bv a long line of 
descent from the primitive wingless ancestors of all the 
insects. The common "fish moth," known to entomolo- 
gists as Lepisma, and its near relation, Machilis (Fig. 57), 
are familiar examples of the truly wingless insects of the 
present time, and if their remote ancestors were as fragile 
and as easily crushed as they, we may see a reason why 
they never left their impressions in the rocks. 

Along with the Carboniferous roaches and the Paleo- 
dictyoptera, there lived a few other kinds of insects, 
many of which are representative of certain modern 



I 94 


groups. Among the latter were dragonflies, and some of 
these must have been of gigantic size, for insects, because 
they attained a wing expanse of fully two feet, while the 
largest of modern dragonflies do not measure more than 
eight inches across the expanded wings. But the length 
of wing of the extinct giant dragonflies does not necessarily 
mean that the bulk of the body was much greater than 
that of the largest insects living today. In general, the 
insects of the past were of ordinary size, the majority of 
them probably matching with insects of the present time. 

The modern dragonflies (Fig. 58) are noted for their 
rapid flight and for the ability to make instantaneous 
changes in the direction of their course while flying. 
These qualities enable them to catch other insects on the 
wing, which constitute their food. Their wings are pro- 
vided with sets of special muscles, such as other insects 
do not possess, showing that the dragonflies are descended 
along a line of their own from their Carboniferous pro- 
genitors. They still retain a character of their ancestors 
in that they are unable to fold the wings flat over the back 
in the manner that most other insects fold their wings 
when they are not using them. The larger dragonflies 
hold the wings straight out from the sides of the body 
when at rest (Fig. 58); but a group of slender dragonflies, 
known as the damselflies (Plate 1, Fig. 2), bring the wings 
together over the back in a vertical plane. 

The dragonflies are usually found most abundantly in 
the neighborhood of open bodies of water. Over the 
unobstructed surface of the water the larger species find 
a convenient hunting ground; but a more important 
reason for their association with water is that they lay 
their eggs either in the water or in the stems of plants 
growing in or beside it. The young dragonflies (Fig. 59) 
are aquatic and must have an easy access to water. They 
are homely, often positively ugly, creatures, having none 
of the elegance of their parents. They feed on other 
living creatures which their swimming powers enable 



them to pursue, and which they capture by means of 
grasping hooks on the end of their extraordinarily long 
underlip (Fig. 134 A), which can be shot out in front of 
the head (B). The great swampy lakes of Paleozoic times 
must have furnished an ideal habitat for dragonflies, and 

it is probable that the most ancient 
dragonflies known had a structure 
and habits not very different from 
those of modern species. 

Another very common insect of 
the present time, which appears 
likewise to be a direct descendant 
of Paleozoic ancestors, is the may- 
fly (Fig. 60). The young mayflies 
(Fig. 61) also live in the water, and 
are provided with gills for aquatic" 
breathing, having the form of flaps 
or filaments situated in a row along 
each side of the body. The adults 
(Fig. 60) are very delicate insects 
with four gauzy wings, and a pair 
of long threadlike tails projecting 
from the rear end of the body. At 
the time of their transformation 
they often issue in great swarms 
from the water, and they are par- 
ticularly attracted to strong lights. 
For this reason large numbers of them come to the cities 
at night, and in the morning they may be seen sitting 
about on walls and windows, where they find themselves 
in a situation totally strange to their native habits and 
instincts. The mayflies do not fold their wings horizon- 
tally, but when at rest bring them together vertically 
over the back (Fig. 60). In this respect they, too, appear 
to preserve a character of their Paleozoic ancestors; 
though it must be observed that the highly evolved 
modern butterflies close their wings in the same fashion. 


Fig. 59. A young dragon- 
fly, an aquatic creature 
that leaves the water only 
when ready to transform 
into the adult (fig. 58) 


The roaches, the dragonflies, and the mayflies attest 
the great antiquity of insects, for since these forms ex- 
isted practically as they are today in Paleozoic times, the 
primitive ancestors of all the insects, of which we have 
no remains in the geological records, must have lived in 
times vastly more remote. However, though we may 
search in vain the paleontological records for evidence 
of the origin and early development of insects, the sub- 
sequent evolution of the higher forms of modern insects 
is clearly shown by the species preserved in eras later 

Fig. 60. A mayfly, representative of another order of primitive 
winged insects having numerous relations in Paleozoic times. 
(Twice natural size) 

than the Carboniferous. Such insects as the beetles, 
the moths, the butterflies, the wasps, the bees, and the 
flies are entirely absent in the older rocks, but make their 
appearance at later periods or in comparatively recent 
times, thus confirming the idea derived from a study of 
their structure that they have been evolved from an- 
cestors more closely resembling the paleodictyopteran 
types of the Carboniferous beds. 

The long line ot descent of the roach, with almost no 
change of form or structure, furnishes material for a 
special lesson in evolution. If evolution has been a 



matter of survival of the fittest, the roach, judged by 
survival, must be a most fit insect. Its fitness, however, 
is of a general nature; it is one that adapts the roach to 
live successfully in many kinds of conditions and circum- 
stances. Most other forms of mod- 
ern insects have been evolved 
through an adaptation to more 
special kinds of habitats and to 
particular ways of living or of feed- 
ing. Such insects we say are 
specialized, while those exemplified 
in the roach are said to be general- 
ized. Survival, therefore, may de- 
pend either on generalization or on 
specialization. Generalized forms 
of animals have a better chance of 
surviving through a series of chang- 
ing conditions than has an animal 
which is specifically adapted to one 
kind of life, though the latter may 
have an advantage as long as con- 
ditions are favorable to it. 

The roaches, therefore, have sur- 
vived to present times, and will 
probably live as long as the earth is 
habitable, because, when driven 
from one environment, they make 
themselves at home in another; but we have all seen how 
the specialized mosquito disappears when its breeding 
places are destroyed. From this consideration we can 
draw some consolation for the human race, if we do not 
mind likening ourselves to roaches; for, as the roach, 
man is a versatile animal, capable of adapting himself to 
all conditions of living, and of thriving in extremes. 

Fig. 6i. A young mayfly, 
a water-inhabiting crea- 
ture. (One-half larger 
than natural size) 

[ 9 8 


In our human society each individual must obtain the 
things necessary for existence; the manner by which he 
acquires them, whether by one trade or another, by this 
means or by that, does not physically matter so long as he 
provides himself and his family with food, clothing, and 
shelter. Exactly so it is with all forms of life. The 
physical demands of living matter make certain things 
necessary for the maintenance of life in that matter, but 
nature has no law specifying that any necessity shall be 
acquired in a certain manner. Life itself is a circum- 
scribed thing, but it has complete freedom ot choice in 
the ways and means of living. 

It is useless to attempt to make a definition of what 
living matter is, or of how it differs from non-living matter, 
for all definitions have failed to distinguish animate from 
non-animate substance. But we all know that living things 
are distinguishable from ordinary non-living things by the 
fact that they make some kind of response to changes in 
the contact between themselves and their environment. 
The "environment," of course, must be broadly inter- 
preted. Biologically, it includes all things and forces that 
in any way touch upon living matter. Not only has every 
plant and animal as a whole its environment, but every 
part of it has an environment. The cells of an animal's 
stomach, for example, have their environment in the blood 
and lymph on one side, the contents of the stomach on the 
other; in the energy of the nerves distributed to them; and 
in the effects of heat and cold that penetrate them. 



The environmental conditions of the life of cells in a 
complex animal are too complicated for an elemental 
study; the elements of life and its basic necessities are bet- 
ter understood in a simple organism, or in a one-celled 
animal; but for purposes of description, it is most con- 
venient to speak of the properties of mere protoplasm. 
All the vital needs of the most highly organized animal are 
present in any part of the protoplasmic substance of which 
it is composed. 

Protoplasm is a chemical substance, or group of sub- 
stances, the structure of which is very complex but is main- 
tained so long as there is no disturbance in the environ- 


Fig. 62. Diagram showing the relation of the germ cells iGCls) and the body 

cells (BCls) in successive generations 

A fertilized germ cell of generation A forms the germ cells and body cells of B, 

a fertilized germ cell of B forms the germ cells and body cells of C, and so on . 

The offspring C of B derives nothing from the body cells of the parent B, but 

both offspring C and parent B have a common origin in a germ cell of A 

ment. Let some least thing happen, however, such as a 
change in the temperature, in the strength of the light, in 
the weight of pressure, or in the chemical composition of 
the surrounding medium, and the protoplasmic molecules, 
in the presence of oxygen, are likely to have the balance of 
their constituent particles upset, whereupon they partly 
decompose by the union of their less stable elements with 
oxygen to form simpler and more permanent compounds. 
The decomposition of the protoplasmic substances, like all 
processes of decomposition, liberates a certain amount of 
energy that had been stored in the making of the molecule, 
and this energy may manifest itself in various ways. If it 

[ 100] 


takes the form of a change of shape in the protoplasmic 
mass, or movement, we say the mass exhibits signs of life. 
The state of being alive, however, is more truly shown if 
the act can be repeated, for the essential property of living 
matter is its power of reverting to its former chemical 
composition, and its ability thus gained of again reacting 
to another change in the environment. In restoring its 
lost elements, it must get these elements anew from the 
environment, for it can not take them back from the sub- 
stances that have been lost. 

Here, expressed in its lowest terms, is the riddle of the 
physical basis of life and of the incentive to evolution in 
the forms of life. Not that these mysteries are any more 
easily understood for being thus analyzed, but they are 
more nearly comprehended. Being alive is maintaining the 
power of repeating an action; it involves sensitivity to 
stimuli, the constant presence of free oxygen, elimination 
of waste, and a supply of substances from which carbon, 
hydrogen, nitrogen, and oxygen, or other necessary ele- 
ments, are readily available for replacement purposes. 
Evolution results from the continual effort of living matter 
to perform its life processes in a more efficient manner, and 
the different groups of living things are the result of the 
different methods that life has tried and found advan- 
tageous for accomplishing its ends. Living organisms are 
machines that have become more and more complex in 
structure, but always for doing the same things. 

It animals may be compared with machines in their 
physical mechanism, they are like them, too, in the fact 
that they wear out and are at last beyond repair. But 
here the simile ends, for when your car will no longer run, 
you must go to the dealer and order a new one. Nature 
provides continuous service by a much better scheme, for 
each organism is responsible for its own successor. This 
phase of life, the replacement of individuals, opens another 
subject involving ways and means, and it, likewise, can be 
understood best in its simpler manifestations. 



The facts of reproduction in animals are not well ex- 
pressed by our name for them. Instead of "reproduc- 
tion," it would be truer to say "repeated production," for 
individuals do not literally reproduce themselves. Genera- 
tions are serially related, not each to the preceding; they 
follow one another as do the buds along the twig of a tree, 

Fk;. 63. The external structure of an insect 
The body of a grasshopper dissected showing the head (//), the thorax (TA), 
and the abdomen {Ab). The head carries the eyes (E), the antennae {Ant), and 
the mouth parts, which include the labrum (Lm), the mandibles {Md), the 
maxiilae IMx), and the labium {Lb). The thorax consists of three segments 
(/, .?, j), the first separate and carrying the first legs (£1), the other two com- 
bined and carrying the wings (W"2, #'.t), and the second and third legs (/.2, Zj). 
The abdomen consists of a series of segments; that of the grasshopper has a 
large tympanal organ {Tm) y probably an ear, on each side of its base. The end 
of the abdomen carries the external organs of reproduction and egg-laying 

and buds on the same twig are identical or nearly so, not 
because one produces the next, but because all are the 
result of the same generative forces in the twig. If the 
spaces of the twig between the buds were shortened until 



one bud became contiguous with the one before, or became 
enveloped by it, a relation would be established between 
the two buds similar to that which exists between succes- 
sive generations of life forms. The so-called parent gen- 
eration, in other words, 
contains the germs of the 
succeeding generation, 
but it does not produce 
them. Each generation 
is simply the custodian 
of the germ cells entrust- 
ed to it, and the "off- 
spring" resembles the 
parent, not because it is 
a chip off the parental 
block, but because both 
parent and offspring are 
developed from the same 
line of germ cells. 

Parents create the 
conditions under which 
the germ cells will de- 
velop; they nourish and 
protect them during the 
period of their develop- 
ment; and, when each 
generation has served 
the purpose of its ex- 
istence, it sooner or 
later dies. But the in- 
dividuals produced from 
for another set of germ 
with themselves, and so 

To express the facts of succession in each specific form of 
animal, then, we should analyze each generation into germ 
cells and an accompanying mass of protective cells which 

Fig. 64. The leg of a young grasshopper, 
showing the typical segmentation of an 

insect's leg 
The leg is supported on a pleural plate 
(PI) in the lateral wall of its segment. 
The basal segment of the free part of the 
leg is the coxa (Cx), then comes a small 
trochanter (TV), next a long femur (F) 
separated by the knee bend from the 
tibia (Ti), and lastly the foot, consisting 
of a sub-segmented tarsus (Tar), and a 
pair of terminal claws (CI) with an ad- 
hesive lobe between them 

its germ cells do the same 
cells produced simultaneously 
on as long as the species 



forms a body, or soma, the so-called parent. Both the 
body, or somatic, cells and the germ cells are formed from a 
single primary cell, which, of course, is usually produced 
by the union of two incomplete germ cells, a spermatozoon 
and an egg. The primary germ cell divides, the daughter 
cells divide, the cells of this division again divide, and the 
division continues indefinitely until a mass of cells is pro- 
duced. At a very early stage of division, however, two 
groups of cells are set apart, one representing the germ 
cells, the other the somatic cells. The former refrain from 
further development at this time; the latter proceed to 
build up the body of the parent. The relation of the 
somatic cells to the germ cells may be represented diagram- 
matically as in Figure 62, except that the usual dual par- 
entage and the union of germ cells is not expressed. The 
sexual form of reproduction is not necessary with all lower 
animals, nor with all generations of plants; in some insects 
the eggs can develop without fertilization. 

The fully-developed mass of somatic cells, whose real 
function is that of a servant to the germ cells, has assumed 
such an importance, as public servants are prone to do, 
that we ordinarily think of it, the body, the active sentient 
animal, as the essential thing. This attitude on our part 
is natural, for we, ourselves, are highly organized masses 
of somatic cells. From a cosmic standpoint, however, no 
creature is important. Species of animals and plants exist 
because they have found ways and means of living that 
have allowed them to survive, but the physical universe 
cares nothing about them — the sunshine is not made for 
them, the winds are not tempered to suit their conven- 
ience. Life must accept what it finds and make the best 
of it, and the question of how best to further its own wel- 
fare is the problem that confronts every species. 

The sciences of anatomy and physiology are a study of 
the methods by which the soma, or body, has contrived to 
meet the requirements imposed upon it by the unchanging 
laws of the physical universe. The methods adopted are as 

[ 104] 



numerous as the species of plants and animals that have 
existed since life began. A treatise on entomology, there- 
fore, is an account of the ways and means of living that 
insects have adopted and perfected in their somatic organ- 
ization. Before discussing insects in particular, however, 
we must understand a little more fully the principal con- 
ditions of living that na- 
ture places on all forms of 

As we have seen, life is 
a series of chemical re- 
actions in a particular 
kind of matter that can 
carry on these reactions. 
A "reaction" is an action; 
and every act of living 
matter involves a break- 
ing down of some of the 
substances in the proto- 
plasm, the discharging of 
the waste materials, and 
the acquisition of new 
materials to replace those 
lost. The reaction is in- 
herent in the physical or 
chemical properties of 
protoplasmic compounds 
and depends upon the 
substances with which 
the protoplasm is sur- 
rounded. It is the func- 
tion of the creature's mechanism to see that the con- 
ditions surrounding its living cells are right for the con- 
tinuance of the cell reactions. Each cell must be 
provided with the means of eliminating waste material 
and of restoring its lost material, since it can not utilize 
that which it has discarded. 

Fig. 65. Legs of a honeybee, showing 

special modifications 
A, outer surface of a hind leg, with a 
pollen basket on the tibia {Th) loaded 
with pollen. B, a fore leg, showing the 
antenna cleaner {a) between the tibia and 
the tarsus, and the long, hairy basal 
segment of the tarsus (/ Tar), which is 
used as a brush for cleaning the body 



With the conditions of living granted, however, proto- 
plasm is still only potentially alive, for there is yet required 
a stimulus to set it into activity. The stimulus for life 
activities comes from changes in the physical forms of 
energy that surround or infringe upon the potentially 
living substance; for, "live" matter, like all other matter, 
is subject to the law of inertia, which decrees that it must 
remain at rest until motion is imparted to it by other 

Md— ■ 

Fig. 66. The head and mouth parts of a grasshopper 

A, facial view of the head, showing the positions of the antennae {Ant), the 
large compound eyes (E), the simple eyes, or ocelli (O), the broad front lip, 
or labrum {Lm) suspended from the cranium by the clypeus {Clp), and the 

bases of the mandibles {Md, Md) closed behind the labrum 

B, the mouth parts separated from the head in relative positions, seen from 
in front: Hphy, hypopharynx, or tongue, attached to base of labium; Lb, labium; 

Lm, labrum; Md, mandibles; Mx, maxillae 

motion. A very small degree of stimulating energy, how- 
ever, may result in the release of a great quantity of 
stored energy. 

The food of all living matter must contain carbon, 
hydrogen, nitrogen, and oxygen. The mechanism of 
plants enables them to take these elements from com- 
pounds dissolved in the water of the soil. Animals must 
get them from other living things, or from the products of 

f 106I 


living things. Therefore, animals principally have de- 
veloped the power of movement; they have acquired grasp- 
ing organs of some sort, a mouth, and an alimentary canal 
for holding the food when once obtained. 

In the insects, the locomotory function is subserved by 
the legs and by the wings. Since all these organs, the three 
pairs of legs and the two pairs of wings, are carried by the 
thorax (Fig. 63, Th), this region of the body is distinctly 
the locomotor center ot the insect. The legs (Fig. 64) are 
adapted, by modifications of structure in different species, 
for walking, running, leaping, digging, climbing, swim- 
ming, and for many varieties of each of these ways of pro- 
gression, fitting each species for its particular mode of 
living and of obtaining its food. The wings ot insects are 
important accessions to their locomotory equipment, 
since they greatly increase their means of getting about, 
and thereby extend their range of feeding. The legs, fur- 
thermore, are often modified in special ways to perform 
some function accessory to feeding. The honeybee, as is 
well known, has pollen-collecting brushes on its front legs 
(Fig. 65 B), and pollen-carrying baskets on its hind legs 
(A). The mantis, which captures other insects and eats 
them alive, has its front legs made over into those efficient 
organs for grasping its prey and for holding the struggling 
victim which have already been described (Fig. 46). 

The principal organs by which insects obtain and ma- 
nipulate their food consist of a set of appendages situated on 
the head in the neighborhood of the mouth, which, in their 
essential structure, are of the nature of the legs, for insects 
have no jaws comparable with those of vertebrate animals. 
The mouth appendages, or mouth parts as they are called, 
are very different in form in the various groups of insects 
that have different feeding habits, but in all cases they 
consist of the same fundamental pieces. Most important 
is a pair of jawlike appendages, known as the mandibles 
(Fig. 66 B, Md), placed at the sides of the mouth (A, Md), 
where they swing sidewise and close upon each other 

[ 107] 


below the mouth. Behind the mandibles is a pair of 
maxillae B, Mx) of more complicated form, fitted rather 
for holding the food than for crushing it. Following the 
maxillae is a large under lip, or labium (Lb), having the 

\ Ant 

Ht - Mai An W 


Fig. 67. Lengthwise section of a grasshopper, showing the general location 
of the principal internal organs, except the respiratory tracheal system and 

the organs of reproduction 
An, anus; Ant, antenna; Br, brain; Cr, crop; Ht, heart; hit, intestine; Mai, 
rhian tubules; Mth, mouth; Oe, oesophagus; SoeGng, suboesophagea! 
ganglion; Vent, stomach wentricu! . entral nerve cord; W y wings 

structure of two maxillae united bv their inner margins. 
A broad flap hangs downward before the mouth to form 
an upper lip, or labrum (Lm). Between the mouth ap- 
pendages and attached to the front of the labium there is a 
large median lobe of the lower head wall behind the mouth, 
known as the hvpophar\tix (Hp 1 

Insects feed, some on solid foods, others on liquids, and 
their mouth parts are modified accordingly. So it comes 
about that, according to their feeding habits, insects may 
be separated into two groups, which, like the iox and the 
stork, could not teed either at the table of the other. Those 
insects, such as the grasshoppers, the crickets, the beetles, 
and the caterpillars, that bite off pieces of food tissue and 
chew them, have the mandibles and the other mouth 
parts of the type described above. Insects that partake 
only of liquids, as do the plant lice, the cicadas, the moths, 
the butterflies, the mosquitoes and other flies, have the 



mouth parts fitted for sucking, or for piercing and sucking. 
Some of the sucking types of mouth parts will be described 
in other chapters (Figs. 121, 163, 183), but it will be seen 
that all are merely adaptations of form based on the ordi- 
nary biting type of mouth appendages. The fossil records 
of the history of insects show that the sucking insects are 
the more recent products of evolution, since all the earlier 
kinds of insects, the cockroaches and their kin, have 
tvpical biting mouth parts. 

The principal thing to observe concerning the organs of 
feeding, in a study of the physiological aspect of anatomy, 
is that they serve in all cases to pass the natural food 
materials from the outside of the animal into the alimen- 
tary canal, and to give them whatever crushing or masti- 
cation is necessary. It is within the alimentary canal, 
therefore, that the next steps toward the final nutrition 
of the animal take place. 

The alimentary canal of most insects is a simple tube 
(Fig. 68), extending either straight through the body, or 

AInt Mint Reo-t 


Fie;. 68. The alimentary canal of a grasshopper 

Ahit, anterior intestine; An t anus; Cr, crop; GC, gastric caeca, pouches of the 
stomach; Hphy, hypopharynx (tongue); Lb, base of labium; Mai, Malpighian 
tubules; Mint, mid-intestine; Mth, mouth; Oe, oesophagus; Reel, hind intestine 
(rectum); SIGI, salivary glands opening by their united ducts at base of hypo- 
pharynx; Vent, ventriculus (stomach) 

making only a few turns or loops in its course. It con- 
sists of three principal parts, of which the middle part is 
the true stomach, or ventriculus {Vent) as it is called by 
insect anatomists. The first part of the tube includes a 

[ 109] 


pharynx immediately behind the mouth, followed by a 
narrower, tubular oesophagus (Oe), after which comes a sac- 
like enlargement, or crop (Cr), in which the food is tem- 
porarily stored, and finally an antechamber to the stomach, 
named the proventriculus. The third part of the alimen- 
tary canal, connecting the stomach with the anal opening, 
is the intestine, usually composed of a narrow anterior 
part, and a wide posterior part, or rectum (Rect). Muscle 
layers surrounding the entire alimentary tube cause the 
food to be swallowed and to be passed along from one 
section to the next toward the rear exit. 

With the taking of the food into the alimentary canal, 
the matter of nutrition is by no means accomplished, for 
the animal is still confronted with the problem of getting 
the nutrient materials into the inside of its body, where 
alone they can be used. The alimentary tube has no 
openings anywhere along its course into the body cavity. 
Whatever food substances the tissues of the animal receive, 
therefore, must be taken through the walls of the tube in 
which they are inclosed, ahd this transposition is accom- 
plished by dissolving them in a liquid. Most of the nutri- 
ent materials in the raw food matter, however, are not 
soluble in ordinary liquids; they must be changed chem- 
ically into a form that will dissolve. The process of get- 
ting the nutrient parts of the raw foodstuff into solution 
constitutes digestion. 

The digestive liquids in insects are furnished mostly 
by the stomach walls or the walls of tubular glands that 
open into the stomach, but the secretion of a pair of large 
glands, called the sa/ivarv glands (Fig. 68, SIGl), which 
open between the mouth parts, perhaps has in some 
cases a digestive action on the food as it is taken into the 

Digestion is a purely chemical process, but it must be 
a rapid one. Consequently the digestive juices contain 
not only substances that will transform the food materials 
into soluble compounds, but other substances that will 



speed up these reactions, for otherwise the animal would 
starve on a full stomach by reason of the slowness of its 
gastric service. The quickening substances of the diges- 
tive fluids are called enzymes, and each kind of enzyme 
acts on only one class of food material. An animal's prac- 
tical digestive powers, therefore, depend entirely upon 
the specific enzymes its digestive liquids contain. Lacking 
this or that enzyme it can not digest the things that depend 
upon it, and usually its instincts are correlated with its 
enzymes so that it does not fill its stomach with food it can 
not digest. A few analyses of the digestive liquids of in- 
sects have been made, enough to show that their digestive 
processes depend upon the presence of the same enzymes as 
those of other animals, including man. 

The grosser digestive substances, in cooperation with 
the enzymes, soon change all the parts of the food ma- 
terials in the stomach that the animal needs for its suste- 
nance into soluble compounds which are dissolved in the 
liquid part of the digestive secretions. Thus is produced 
a rich, nutrient juice within the alimentary canal which 
can be absorbed through the walls of the stomach and intes- 
tine and can so enter the closed cavity of the body. The 
next problem is that of distribution, for still the food ma- 
terials must reach the individual cells of the tissues that 
compose the animal. 

The insect's way of feeding, of digesting its food, and of 
absorbing it is not essentially different from that of the 
higher animals, including ourselves, for alimentation is a 
very old and fundamental function of all animals. Its 
means of distributing the digested food within its body, 
however, is quite different from that of vertebrates. The 
absorbed pabulum, instead of being received into a set of 
lymphatic vessels and from these sent into blood-filled 
tubes to be pumped to all parts of the organism, goes 
directly from the alimentary walls into the general body 
cavity, which is filled with a liquid that bathes the inner 
surfaces of all the body tissues. This body liquid is called 



the "blood" ot the insec 
yellow-tinted lymph. It 




Fig. 69. Diagram of the 
typical structure of an insect's 
heart and supporting dia- 
phragm, with the course of the 
circulating blood marked by 

Ao, aorta, or anterior tubular 
part of the heart without 
lateral openings; Dph, mem- 
branous diaphragm; Ht, ante- 
rior three chambers of the 
heart, which usually extends 
to the posterior end of the 
body; Mel, muscles of dia- 
phragm, the fibers spreading 
from the body wall to the 
heart; Ost, ostium, or oneof the 
lateral openings into the heart 

t, but it is a colorless or slightly 
is kept in motion, however, by a 
pulsating vessel, or heart, lying 
in the dorsal part of the body; 
and by this means the food, now 
dissolved in the body liquid, is 
carried into the spaces between 
the various organs, where the 
cells of the latter can have access 
to it. 

The heart ot the insect is a 
slender tube suspended along the 
midline of the back close to the 
dorsal wall of the body (Fig- 67, 
Ht). It has intake apertures 
along its sides (Fig. 69, Ost), and 
its anterior end opens into the 
body cavity. It pulsates for- 
ward, by means of muscle fibers 
in its walls, thereby sucking the 
blood in through the lateral 
openings and discharging it by 
way of the front exit. An im- 
perfect circulation of the blood 
is thus established through the 
spaces between the organs of the 
body cavity, sufficient for the 
purposes of so small an animal as 
an insect. 

The final act of nutrition comes 
now when the blood, charged 
with the nutrient materials ab- 
sorbed from the digested food 
in the alimentary canal, brings 
these materials into contact with 
the inner tissues. The tissue 
cells, by the inherent power of 



all living matter (which depends on the laws of osmosis 
and on chemical affinity), take for themselves whatever 
they need from the menu offered by the blood, and with 
this matter they build up their own substance. It is 
evident, therefore, that the blood must contain a suffi- 
cient quantity and variety of dietary elements to satisfy 
all possible cell appetites; that the stomach's walls and 
their associated glands must furnish the enzymes appro- 
priate for making the necessary elements available from 
the raw food matter in the stomach; and, finally, that it 
must be a part of the instincts of each animal species to 
consume such native foodstuffs of its environment as will 
supply every variety of nourishing elements that the cells 

As we have seen, the demand for food comes from the 
loss of materials that are decomposed in the tissues during 
cell activity. Better stated, perhaps, the chemical break- 
down within the cell is the cause of the cell activity, or is 
the cell activity itself. The way in which the activity is 
expressed does not matter; whether by the contraction of a 
muscle cell, the secretion of a gland cell, the generation of 
nerve energy bv a nerve cell, or just the minimum activity 
that maintains life, the result is the same always — the loss 
of certain substances. But, as with most chemical reduc- 
tion processes, the protoplasmic activity depends upon the 
presence of available oxygen; for the decomposition of the 
unstable substances of the protoplasm is the result of the 
affinity of some of their elements for oxygen. Conse- 
quently, when the stimulus for action comes over a nerve 
from a nerve center, a sudden reorganization takes place 
between these protoplasmic elements and the oxygen 
atoms which results in the formation of water, carbon 
dioxide, and various stable nitrogenous compounds. 

The substances discarded as a result of the cell activi- 
ties are waste products, and must be eliminated from the 
organism for their presence would clog the further activity 
of the cells or would be poisonous to them. The animal, 



therefore, must have, in addition to its mechanisms for 
bringing food and oxygen to the cells, a means for the re- 
moval of wastes. 

The supplying of oxygen and the removing of carbon 
dioxide and some of the excess water are accomplished by 
respiration. Respiration is primarily the exchange of gases 
between the cells of the body and the outside air. If an 
animal is sufficiently small and soft-skinned, the gas ex- 
change can be made directly by diffusion through the skin. 
Larger animals, however, must have a device for conveying 
air into the body where the tissues will have closer access 
to it. It will be evident, then, that there is not neces- 
sarily only one way of accomplishing the purposes of 

Vertebrate animals inhale air into a sac or pair of sacs, 
called the lungs, through the very thin walls of which the 
oxygen and carbon dioxide can go into and out of the 
blood respectively. The blood contains a special oxygen 
carrier in the red matter, hemoglobin, of its red corpuscles, 
by means of which the oxygen taken in from the air is 
transported to the tissues. The carbon dioxide is carried 
from the tissues partly by the hemoglobin, and partly 
dissolved in the blood liquid. 

Insects have no lungs, nor have they hemoglobin in their 
blood, which, as we have seen, is merely the liquid that fills 
the spaces of the body cavity between the organs. Insects 
have adopted and perfected a method of getting air dis- 
tributed through their bodies quite different from that of 
the vertebrates. They have a system of air tubes, called 
tracheae (Fig. 70), opening from the exterior by small 
breathing pores, or spiracles (Sp), along the sides of the 
body, and branching minutely within the body to all parts 
of the tissues. By this means the air is conveyed directly 
to the parts where respiration takes place. There are 
usually in insects ten pairs of spiracles, two on the sides of 
the thorax, and eight on the abdomen. The spiracles 
communicate with a pair of large tracheal trunks lying 

[n 4 ] 


along the sides of the body (Fig. 70), and from these 
trunks are given off branches into each body segment and 
into the head, which go to the alimentary canal, the heart, 
the nervous system, the muscles, and to all the other 
organs, where they break up into finer branches that 
terminate in minute end tubes going 
practically to every cell of the body. 

Many insects breathe by regular 
movements of expansion and contrac- 
tion of the under surface of the abdo- 
men, but experimenters have not yet 
agreed as to whether the air goes in 
and out of the same spiracles or 
whether it enters one set and is ex- 
pelled through another. It is probable 
that the fresh air goes into the smaller 
tracheal branches principally by gas 
diffusion, for some insects make no 
perceptible respiratory movements. 

The actual exchange of oxygen from 
the air and carbon dioxide from the 
tissues takes place through the thin 
walls of the minute end tubes of the 
tracheae. Since these tubes lie in im- 
mediate contact with the cell surfaces 
the gases do not have to go far in 
order to reach their destinations, and 
the insect has little need of an oxygen 
carrier in its blood — its whole body, 
practically, is a lung. And yet some 
investigations have made it appear 
likely that the insect blood does con- 
tain an oxygen carrier that functions 
in a manner similar to that of the 
hemoglobin ot vertebrate blood, 
though the importance of oxygen 
transportation in insect physiology has 

Fig. 70. Respiratory 
system of a caterpillar. 
The external breathing 
apertures, or spiracles 
(Sp, Sp), along the 
sides of the body open 
into lateral tracheal 
trunks (a, a), which 
are connected crosswise 
by transverse tubes 
(b, b) and give off mi- 
nutely branching tra- 
cheae into all parts of 
the head (H) and body 



not been determined. In any case, the tracheal method 
of respiration must be a very efficient one; for, consider- 
ing the activity of insects, especially the rate at which the 
wing muscles act during flight, the consumption of oxygen 
must at times be pretty high. 

The activity of insects depends very much, as every one 
knows, upon the temperature. We have all observed how 
the house flies disappear upon the first cold snap in the fall 
and then surprise us by showing up again when the weather 
turns warm, just after we have taken down the screens. 
All insects depend largely upon external warmth for the 
heat necessary to maintain cellular activity. While their 
movements produce heat, they have no means of con- 
serving this heat in their bodies, as have "warm-blooded" 
animals. That insects radiate heat, however, is very 
evident from the high temperature that bees can maintain 
in their hives during winter by motion of the wings. All 
insects exhale much water vapor from their spiracles, an- 
other evidence of the production of heat in their bodies. 

The solid matter thrown off from the cells in activity is 
discharged into the blood. These waste materials, which 
are mostly compounds of nitrogen in the form of salts, 
must then be removed from the blood, for their accumula- 
tion in the body would be injurious to the tissues. In 
vertebrate animals, the nitrogenous wastes are eliminated 
by the kidneys. Insects have a set of tubes, comparable 
with the kidneys in function, which open into the intestine 
at the junction of the latter with the stomach (Fig. 68, 
Mai), and which are named, after their discoverer, the 
Malpighian tubules. These tubes extend through the prin- 
cipal spaces of the body cavity, where they are looped 
and tangled like threads about the other organs and are 
continually bathed in the blood. The cells of the tube 
walls pick out the nitrogenous wastes from the blood and 
discharge them into the intestine, whence they are passed 
to the exterior with the undigested food refuse. 

We thus see that the inside of an insect is not an unor- 

f 116I 


ganized mass of pulp, as believed by those people whose 
education in such matters comes principally from under- 
foot. The physical unity of all forms of life makes it neces- 
sary that every creature must perform the same vital 
functions. The insects have, in many respects, adopted 
their own wavs of accomplishing these functions, but, as 
already pointed out, the means of doing a thing does not 
count with nature so long as the end results are attained. 
The essential conditions are the supply of necessities and 
the removal of wastes. 

The body of a complex animal may be likened to a great 
factory, in which the individual workers are represented by 
the cells, and groups of workers by the organs. That the 
factory may accomplish its purpose, the activities of each 
worker must be coordinated with those of all the other 
workers by orders from a directing office. Just so, the ac- 
tivities of the cells and organs of the animal must be con- 
trolled and coordinated; and the directing office of the 
animal organization is the central nervous system. The 
work of almost every cell in the body is ordered and con- 
trolled by a "nerve impulse" sent to it over a nerve fiber 
from a nerve center. 

The inner structure of the nervous tissues and the work- 
ing mechanism of the nerve centers are essentially alike in 
all animals, but the form and arrangement of the nerve 
tissue masses and the distribution of the nerve fibers may 
differ much according to the plan of the general body or- 
ganization. The insects, instead of following the verte- 
brate plan of having the central nerve cord along the back 
inclosed in a bony sheath, have found it just as well for 
their purposes to have the principal nerve cord lying free in 
the lower part of the bodv (Fig- 67, VNC). In the head 
there is a brain (Figs. 67, 72, Br) situated above the 
oesophagus (Fig. 67, Oe), but it is connected by a pair of 
cords with another nerve mass below the pharynx in the 
lower part of the head (SoeGng). From this nerve mass 
another pair of nerve cords goes to a third nerve mass 



lying against the 
lower wall of the 
first body seg- 
ment (Fig. 72, 
Gng 1), which is 
ed with a fourth 
mass in the sec- 
ond segment, and 
so on. The cen- 
tral nervous sys- 
tem of the insect 
thus consists of 
a series of small 
nerve masses 
united by double 
nerve cords. The 
nerve masses are 
known as gan- 
glia {Gng), and 
the uniting cords 
are called the 
connectives (Fig. 
71, Con). Typi- 
cally there is a 
ganglion for each 
of the first 
eleven body seg- 
ments, besides 
the brain and 
the lower gan- 
glion of the head. 
The brain of an insect (Fig. 71) has a highly complex 
internal structure, but it is a less important controlling 
center than is the brain of a vertebrate animal. The other 
ganglia have much independence of function, each giving 
the stimuli for movements of its own segment. For this 

r 1 

1 -* 



^ J 


_ _T- 




2 Br 







fi 1 






1 V 


]\, . CceCon. 


J V 






LmNv.. > 

J « 






jllj^y-i •SixGng- 

Fig. 71. The nervous system of the head of a grass- 
hopper, as seen by removal of the facial wall 
AntNv, antenna! nerve; /Br, sBr.jBr, the three parts 
of the brain; CoeCon, circumoesophageal connectives; 
jCom, suboesophageal commissure of the third lobes 
of the brain; FrGng, frontal ganglion; FrCcm, frontal 
ganglion connective with the brain; LbNv, labial 
nerve; LmNv, labral nerve; MdNv, mandibular nerve; 
MxNv, maxillary nerve; 0, simple eye; OpL, optic 
lobe connected with the brain; RNv, recurrent nerve; 
SoeGng, suboesophageal ganglion 



reason, the head of an insect may be cut off and the rest 
of the creature may still be able to walk and to do various 
other things until it dies of starvation. Similarly, with 
some species, the abdomen may be severed and the insect 
will still eat, though the food runs out of the cut end of the 
alimentary canal. The detached abdomen may lay eggs, 
if properly stimulated. Though the insect thus appears to 
be largely a creature of automatic regulations, acts are not 
initiated without the brain, and full coordination of the 
functions is possible only when the entire nervous system 
is intact. 

The active elements of the nerve centers are nerve cells; 
the nerve fibers are merely conducting threads extended 
from the cells. If the nerve force that stimulates the other 
kinds of cells into activity comes from nerve cells, the 
question then arises as to whence comes the primary 
stimulus that activates the nerve cells. We must discard 
the old idea that nerve cells act automatically; being mat- 
ter, they are subject to the laws of matter — they are inert 
until compelled to act. The stimulus of the nerve cells 
comes from something outside of them, either from the 
environmental forces of the external world or from sub- 
stances formed by other cells within the body. 

Nothing is known definitely of the internal stimuli of 
insects, but there can be no doubt that substances are 
formed by the physiological activities of the insect tissues, 
similar to the hormones, or secretions of the ductless glands 
of other animals, that control action in other organs either 
directly or through the nervous system. Thus, some in- 
ternal condition must prompt the insect to feed when its 
stomach is empty, and the entrance of food into its pharynx 
must stimulate the alimentary glands to prepare the diges- 
tive juices. Probably a secretion from the reproductive 
organs of the female, when the eggs are ripe in the ovaries, 
gives the stimulus for mating, and later sets into motion 
the reflexes that govern the laying of the eggs. The cater- 
pillar spins its cocoon at the proper time for doing so; the 



Gng-V- - 


, -Proc 


Fig. 72. The general nervous system of a grass- 
hopper, as seen from above 
Ant, antenna; Ao, aorta; fir, brain; Or, cercus; E, 
compound eye; Gng/, ganglion of prothorax; 
Gng2, ganglion of mesothorax; Gngj+I+Il+III, 
compound ganglion of metathorax, comprising 
the ganglia belonging to the metathorax and the 
first three abdominal segments; GnglV — GngVIH, 
ganglia of the fourth to eighth abdominal seg- 
ments; 0, ocelli; Proc, proctodeum, or posterior 
part of alimentary canal; Sa, suranal plate; 
Stgll — X, second to tenth segments of abdomen; 
SoeGng, suboesophageal ganglion; Stom, stomo- 
deum, or anterior part of alimentary canal 

stimulus, most like- 
ly, comes from the 
products of physio- 
logical changes be- 
ginning to take place 
in the body that will 
soon result in the 
transformation of 
the caterpillar into 
a chrysalis, a stage 
when the insect 
needs the protection 
of a cocoon. These 
activities of insects 
we call instincts, but 
the term is simply a 
cover for our ignor- 
ance of the processes 
that cause them. 

External stimuli 
are things of the 
outer environment 
that affect the living 
organism. They in- 
clude matter, elec- 
tromagnetic energy, 
and gravity; but the 
known stimuli do 
not comprise all the 
activities of matter 
or of the "ether." 
The common stimuli 
are: pressure of 
solids, liquids, and 
gases; humidity; 
chemical qualities 
(odors and tastes); 

I 120 


sound, heat, light, and gravity. Most of these things stim- 
ulate the nerve centers indirectly through nerves connected 
with the skin or with specialized parts of the skin called 
sense organs. An animal can respond, therefore, only to 
those stimuli, or to the degrees of a particular stimulus, to 
which it is sensitive. If, for example, an animal has no re- 
ceptive apparatus for sound waves, it will not be affected 
by sound; if it is not sensitized to certain wave lengths of 
light, the corresponding colors will not stimulate it. There 
are few kinds of natural activities in the environment that 
animals do not perceive; but even our own perceptive 
powers fall far short of registering all the degrees of any 
activity that are known to exist and which the physicist 
can measure. 

Insects respond to most of the kinds of stimuli that we 
perceive by our senses; but if we say that they see, hear, 
smell, taste, or touch we make the implication that insects 
have consciousness. It is most likely that their reactions 
to external stimuli are for the most part performed un- 
consciously, and that their behavior under the effect of a 
stimulus is an automatic action entirely comparable to 
our reflex actions. Behavioristic acts that result from 
reflexes the biologist calls tropisms. Coordinated groups 
of tropisms constitute an instinct, though, as we have 
seen, an instinct may depend also on internal stimuli. It 
can not be said that consciousness does not play a small 
part in determining the activities of some insects, es- 
pecially of those species in which memory, i.e., stored 
impressions, appears to give a power of choice between 
different conditions presented. The subject of insect 
psychology, however, is too intricate to be discussed 

The phases of life thus far described, the complexity 
of physical organization, the response to stimuli, the 
phenomena of consciousness from their lowest to their 
highest manifestations, all pertain to the soma. Yet, 
somehow, the plan of the edifice is carried along in the 

I 121 1 


germ cells, and by them the whole somatic structure is 
rebuilt with but little change of detail from generation to 
generation. This phase of life activity is still a mystery 
to US; for no attempted explanation seems adequate to 
account for the organizing power resident in the germ 
cells that accomplishes the familiar facts of repeated 





Fie. 73. Diagrams of the internal organs of reproduction in insects 

A, the female organs, comprising a pair of ovaries {Ov), each composed of a 
group of egg tubules (ot), a pair of oviducts (DOv), and a median outlet tube, or 
vagina (fg) t with usually a pair of colleterial glands (ClGl) discharging into 
the vagina, and a sperm receptacle, or spermatheca (Spm), opening from the 

upper surface of the latter 

B, the male organs, comprising a pair of testes (Tes) composed of spermatic 
tubules, a pair of sperm ducts, or vasa deferentia (^D), a pair of sperm vesicles 
(yS), and an outlet tube, or ductus ejaculatorius {DE), with usually a pair of 

mucous glands (MG1) discharging into the ducts of the sperm vesicles 

development which we call reproduction. When we can 
explain the repetition of buds along the twig, we may 
have a key to the secret of the germ cells — and possibly 
to that of organic evolution. 

The organs that house the germ cells in the mature 
insect consist of a pair of ovaries in the female (Fig. 73 A, 
Ov) in which the eggs mature, and of a pair of testes in the 



male (B, Tes) in which the spermatozoa reach their com- 
plete growth. Appropriate ducts connect the ovaries or 
the testes with the exterior near the rear end of the body. 
The female usually has a sac connected with the egg duct 
(A, Spm) in which the sperm, received at mating, are 
stored until the eggs are ready to be laid, when they are 


i / / / 

Fig. 74. The ovipositor of a long-horned grasshopper, a member of the katydid 
family, showing the typical structure of the egg-laying organ of female insects 

A, the ovipositor (Ovp) in natural condition, projecting from near the posterior 

end of the body 

B, the parts of the ovipositor separated, showing the six component pieces, 
two arising from the eighth abdominal segment {VIII), and four from the ninth 
(IX). An, anus; Cer, cerci; IX, ninth abdominal segment; Ovp, ovipositor; VgO, 
vaginal opening; VIII, eighth abdominal segment; X, tenth abdominal segment 

extruded upon the latter and bring about fertilization. 
The egg cells ordinarily are all alike, but the spermatozoa 
are of two kinds; and according to the kind of sperm re- 
ceived by any particular egg, the future individual will be 
male or female. 

[ 123] 


The germ cells accompanying each new soma undergo a 
series of transformations within the parent body before 
thev themselves are capable of accomplishing their pur- 
pose. They multiply enormously. With some animals, 
only a few of them ever produce new members of the race; 
but with insects, whose motto is "safety in numbers," 
each species produces every season a great abundance of 
new individuals, to the end that the many forces arrayed 
against them may not bring about their extermination. 

The world seems full of forces opposed to organized life. 
But the truth is, all organization is an opposition to 
established forces. The reason that the forms of life now 
existing have held their places in nature is that they have 
found and perfected ways and means of opposing, for a 
time, the forces that tend to the dissipation of energy. 
Life is a revolt against inertia. Those species that have 
died out are extinct, either because they came to the end 
of their resources, or because they became so inflexibly 
adapted to a certain kind -of life that thev were unable to 
meet the emergency of a change in the conditions that 
made this life possible. Efficiency in the ordinary means 
of living, rather than specialization for a particular way of 
living, appears to be the best guarantee of continued 

[I2 4 l 


It was the custom, not long ago, to teach the inexperienced 
that the will can achieve whatever ambition may desire. 
"Believe that you can, and you can, if only you work hard 
enough"; this was the subject of many a maxim very en- 
couraging, no doubt, to the young adventurer, but just as 
likely to lead to a bench in Union Square as to a Fifth 
Avenue studio or a seat in the Stock Exchange. 

Now it is the fashion to give us mental tests and voca- 
tional suggestions, and we are admonished that it is no 
use trying to be one thing if nature has made us for some- 
thing else. This is sound advice; the only trouble is the 
difficulty of being able to detect at an early age the char- 
acters that are to distinguish a plumber from a doctor, a 
cook from an actress, or a financier from an entomologist. 
Of course, there really are differences between all classes 
of people from the time they are born, and a fine thing 
it would be if we could know in our youth just what each 
one of us is designed to become. In the present chap- 
ter we are to learn that certain insects appear to have 
achieved this very thing. 

The termites are social insects; consequently in study- 
ing them, we shall be confronted with questions of con- 
duct. Therefore, it will be well at the outset to look 
somewhat into the subject of morality; not, be assured, 
to learn any of its irksome precepts, but to discover its 
biological significance. 

Right and wrong, some people think, are general ab- 
stractions that exist in the very nature of things. They 



Fig. 75. A common 

are, on the contrary, specific attributes that are condi- 
tioned by circumstances. An act that is right is one in 
accord with the nature of the creature performing it; that 
which is wrong is a contrary act. Hence, what is right for 
one species of animal may be wrong tor another, and the 

The conduct of adult human individuals, according to 
human standards of right and wrong, we call morals; the 
similar conduct of other animals is a part of what biolo- 
gists call behavior. But we unconsciously recognize some- 
thing in common between morals and behavior when we 
speak of the acts of a child, which we call his behavior 

rather than his morals. 
Behavior, in other 
words, we regard as in- 
volving less of personal 
responsibility than mo- 
rality. Hence we say 
that animals and chil- 
species of termite of Jren behave, but that 

eastern North America j 1 l i 

inhabiting dead wood, adult human beings con- 

Reticulilermes fiampes. sc i OU sly do right Or 

£.2hW.S£ wro "g' Yet, the two 
modes of action accom- 
plish similar results: if the child behaves 
properly, his actions are right; if the 
adult has a properly developed moral 
sense, he too does the right thing, or at 
least he refrains from doing the wrong 
thing unless misguided by circumstances 
or by his reasoning. 

Animals other than the human, it 
appears, generally do what is right from their standpoint; 
but their actions, we say, are instinctive. Some will insist 
that the terms "right" and "wrong" can have no appli- 
cation to them. Substitute then, if you please, the 
expression "appropriate or non-appropriate to the ani- 



mal's way of living." And still, our morality will analyze 
into the same two elements; our acts are right or wrong 
according as they are appropriate or non-appropriate to 
our way of living. 

The difference between human actions and those of 
other animals is not essentially in the acts themselves, but 
in the methods by which they are brought about. Animals 
are controlled by instincts, mostly; man is controlled by a 
conscious feeling that he should do this or that — "con- 
science," we call it — and his specific actions are the result 
of his reasoning or teaching as to what is right and what is 
wrong, excepting, of course, the acts of perverted indi- 
viduals who lack either a functional conscience or a well- 
adjusted power of reason, or of individuals in whom the 
instincts of an earlier way of living are still strong. The 
general truth is clear, however, that in behavior, as in 
physiology, there is not just one way of arriving at a 
common result, and that nature may employ quite dif- 
ferent means for determining and activating conduct in 
her creatures. 

Since right and wrong, then, are not abstract prop- 
erties, but are terms expressing fitness or non-fitness, 
judged according to circumstances, or an animal's way of 
living, it is evident that the quality of actions will differ 
much according to how a species lives. Particularly 
will there be a difference in the necessary behavior of 
species that live as individuals and of those that live as 
groups of individuals. In other words, that which may 
be right for an individualistic species may be wrong for 
a communal species; for, with the latter, the group re- 
places the individual, and relations are now established 
within the group, or pertaining to the group as a whole, 
that before applied to the individual, while relations that 
formerly existed between individuals become now rela- 
tions between groups. 

The majority of animals live as individuals, each 
wandering here and there, wherever its fancy leads or 



wherever the food supply attracts it, recognizing no ties 
or responsibilities to others of its species and contending 
with its fellows, often in deadly combat, for whatever 


vantage it can gam. 

Fig. 76. Termite work in a piece of 
wood. Tunnels following the grain are 
made by species of Reticulilermes, the com- 
mon underground termites of the eastern 
United States 

A few animals are communistic 
or social in their mode 
of life; notably so are 
man and certain insects. 
The best-known exam- 
ples of social insects are 
the ants and some of the 
bees and wasps. The 
termites, however, con- 
stitute another group of 
social insects ot no less 
interest than the ants 
and bees, but whose hab- 
its have not been so long 

More familiarly to 
some people, termites are 
known as "white ants." 
But since they are not 
ants, nor always white 
or even pale in color, we 
should discard this mis- 
leading and unjustifiable 
appellation and learn to 
know the termites by the 
name under which thev 
are universally known to 

Jf you split open an 
old board that has been 
lying almost anywhere 
on the ground for some 
time, or if, when out in 
the woods, you cut into 



a dead stump or a log, you are more than likely to find 
it tunneled all through with small tubular galleries running 
with the grain of the wood, but everywhere connected 
crosswise by small openings or short passages. Within 
the exposed galleries there will be seen numerous small, 
pale, wingless insects running here and there in an effort 
to conceal themselves. These insects are termites. 
They are the miners or the descendants of miners that 
have excavated the tunnels in which they live. Not all 
of the galleries in the nest are open runways, many of 
them being packed solidly with small pellets of refuse. 

If the termites confined themselves to useless wood, 
they would be known only as interesting insects; but 
since they often extend their operations into fence posts, 
telegraph poles, the woodwork of houses, and even into 
furniture, they have placed themselves among the de- 
structive insects and have acquired an important place 
in the pages of economic entomology. Stored papers, 
books, cloth, and leather are not exempt from their at- 
tack. In the United States it not infrequently happens 
that the flooring or other wooden parts of buildings must 
be replaced, owing to the unsuspected work of termites; 
and piled lumber is especially liable to invasion by these 
insidious insects. But in tropical countries the termites 
are far more numerous than in temperate regions, and 
are vastly more destructive than they are with us. Their 
seclusive habits make the termites a particularly vexa- 
tious pest, because they have usually accomplished an 
irreparable amount of damage before their presence is 
known or suspected. The economic entomologist study- 
ing termites gives most of his attention, therefore, to 
devising methods of preventing the access of the insects 
to all wooden structures that they might destroy. 

The work of termites and the ways and means that 
have been contrived to prevent their ravages have been 
described in many agricultural publications, and the 
reader whose tastes are purely practical is referred to 

[ 129] 


the latter for information. Here we will look more closely 
into the lives of the termites themselves to see what 
lessons we may learn from these creatures that have 
adopted something of our own way of living. 

When a termite nest is broken open, it does not appear 
that there is much of an organization among the insects 

Fig. 77. Reticulitermes flavxpcs (much enlarged) 

A, a mature worker. B, a mature soldier. C, a young termite. 

D, an immature winged form 

hurrying to take refuge in the recesses o( the galleries, 
but neither when a bomb strikes one of our own dwellings 
is there probably much evidence of order within. The 
most casual observation of the termites, however, will 

[ I3°] 


show something of interest concerning them. In the 
first place, it is to be seen that not all the members of the 
colony are alike. Some, usually the greater number, are 
small, ordinary, soft-bodied, wingless insects with rounded 
heads and inconspicuous jaws (Figs. 75 D, 77 A). Others, 
less numerous, have bodies like the first, and are also 
wingless, but their heads are relatively of enormous size 
and support a pair of large, strong jaws projecting out 
in front (Figs. 75 C, 77 B). The individuals of the latter 
kind are known as soldiers, and the name is not entirely 
fanciful, since fighting is not necessarily the everyday 
occupation of one in military service. The others, the 
small-headed individuals, are called workers, and they 
earn their title literally, for, even with their small jaws, 
they do most of the work of excavating the tunnels, and 
they perform whatever other labors are to be done within 
the nest. 

Both the workers and the soldiers are males and females, 
but so far as reproductive powers go, they may be called 
"neuters," since their reproductive organs never mature 
and they take no part in the replenishment of the colony. 
In most species of termites the workers and the soldiers 
are blind, having no eyes or but rudiments of eyes. In 
a few of the more primitive termite genera, workers are 
absent, and in the higher genera they may be of two 
types of structure. The large jaws of the soldiers (Fig. 
78 A) are weapons of defense in some species, and the 
soldiers are said to present themselves at any break in the 
walls of the nest ready to defend the colony against in- 
vasion. In some species, the soldiers have a long tubular 
horn projecting forward from the face (Fig. 78 B), through 
which opens the duct of a gland that emits a sticky, 
semiliquid substance. This glue is discharged upon an 
attacking enemy, who is generally an ant, and so thor- 
oughly gums him up that he is rendered helpless — a 
means of combat yet to be adopted in human warfare. 
The facial gland is developed to such efficiency as a 



weapon in many species of one termite family that the 
soldiers of these species have no need of jaws, and their 
mandibles have become rudimentary. In all cases, the 
military specialization of the soldiers has rendered them 
incapable of feeding themselves, and they must depend 
on the workers for food. 

In addition to the soldiers and the workers, there 
would probably be seen within the termite nest, at cer- 


Fig. 78. Two forms of defensive organs of termite soldiers 
A, head of soldier of Termopsis, showing the highly developed mandibles \Md) , 
and the great muscles within the head (admd) that close them. B, a soldier of 
Nasutitermes (from Banks and Snyder); the head has small jaws but is provided 
with a long snoutlike horn through which is ejected a gummy liquid used for 


tain seasons of the year, many individuals (Fig. 77 D) 
that have small wing rudiments on their thoracic seg- 
ments. As the season advances, the wing pads of these 
individuals increase in length, until at last they become 
long, gauzy, fully-developed wings extending much beyond 
the tip of the body (Figs. 75 A, B, 79). The color of the 
body also becomes darker, and finally blackish when the 
insects are mature. Then, on some particular day, the 

] 3 2 


whole winged brood issues from the nest in a great swarm. 
Since insects are normally winged creatures, it is evident 
that these flying termites represent the perfect forms of 
the termite colony — they are, in fact, the sexually mature 
males and females. 

The several forms of individuals in the termite com- 
munity are known as castes. 

An intensive search through the galleries of a termite 
nest might reveal, besides workers, soldiers, and the 
members of the winged brood in various stages of devel- 
opment, a few individuals of still different kinds. These 
have heads like the winged forms, but rather larger bodies; 
some have short wing rudiments (Fig. 80), others have 
none; and finally there are two individuals, a male and 
a female, bearing wing stubs from which, evidently, 
fully-formed wings have been broken off. The male of 
this last pair is just an ordinary-looking, though dark- 
bodied termite 
(Fig. 82 A); but 
the female is dis- 
tinguished from 
all the other mem- 
bers of the colony 
by the great size 
of her abdomen 

Through the in- 
vestigations of 
entomologists it is 
known that the 
short-winged . and 
wingless individu- 
als of this group comprise both males and females that 
are potentially capable of reproduction, but that in 
general all the eggs of the colony are actually produced 
by the large-bodied female, whose consort is the male 
that has lost his wings. In other words, this fertile 

Fig. 79. Adult winged caste of Reticulitermcs tibialis, 

wings shown on one side of the body only. (From 

Banks and Snyder) 



female corresponds with the "queen" in a hive of bees; 
but, unlike the queen bee, the queen termite allows the 
"king" termite to live with her throughout her life in the 

It appears, then, that the termite community is a com- 
plex society of castes, for we must now add to the worker 
and soldier castes the two castes of potentially repro- 
ductive individuals, and the "royal" or actual producing 
caste, consisting of the king and the queen. We are thus 
introduced to a social state quite different from anything 
known in our own civilization, for, though we may have 
castes, the distinctions between them are largely matters 
of polite concession by the less aspiring members of the 
community. We theoretically claim that we are all born 
equal. Though we know that this is but a gratifying 
illusion, our inequalities at least do not go by recognized 
caste. A termite, however, is literally born into his 
place in society and eventually has his caste insignia in- 
delibly stamped in the structure of his body. This state 
of affairs upsets all our ideas and doctrines of the funda- 
mental naturalness and rightness of democracy; and, if 
it is true that nature not only recognizes castes but 
creates them, we must look more closely into the affairs 
of the termite society to see how such things may come 

Let us go back to the swarm of winged males and 
females that have issued from the nest. The birds are 
already feeding upon them, for the termites' powers of 
flight are at best feeble and uncertain. The winds have 
scattered them, and in a short time the fluttering horde 
will be dispersed and probably most of its members will 
be destroyed one way or another. The object of the 
swarming, however, is the distribution of the insects, and, 
if a few survive, that is all that will be necessary for the 
continuance of the race. When the fluttering insects 
alight they no longer have need of their wings, and by 
brushing against objects, or bv twisting the body until 


the tip of the abdomen comes against the wing bases, 
the encumbering organs are broken off. It may be 
observed that there is a suture across the base of each 
wing just to make the breaking easy. 

The now wingless termites, being young males and 
females just come to maturity, naturally pair off; but 

Fig. 80. The second form, or short-winged reproductive caste, 

of Riticulilermes tibialis. (From Banks and Snyder) 

A, male. B, female 

not for a companionate marriage, which, it must be 
confessed, is the popular form of matrimony with most 
insects. The termites take the vows of lifetime fidelity, 
or "till death do us part," for with the female termite 
intensive domesticity and maternity are the ruling pas- 
sions. To find a home site and there found a colony is 
her consuming ambition, and, whether the male likes 
it or not, he must accept her conditions. The female, 
therefore, searches out a hole or a crevice in a dead tree 
or a decayed stump, or crawls under a piece of wood 
lying on the ground, and the male follows. If the site 



proves suitable, the female begins digging into the wood 
or into the ground beneath it, using her jaws as exca- 
vating tools, perhaps helped a little by the male, and 
soon a shaft is sunk at the end of which a cavity is hol- 
lowed out of sufficient size to accommodate the pair and 
to serve the purposes of a nest where true matrimony 
may begin. 

Naturally it would be a very difficult matter to follow 
the whole course of events in the building of a termite 
community from one of these newly married pairs, tor 
the termites live in absolute seclusion and any disturbance 
of their nests breaks up the routine of their lives and 
frustrates the efforts of the investigator. Many phases, 
however, of the life and habits of our common eastern 
United States termites, particularly of species belonging 
to the genus Reticulitermes, have been discovered and 
recorded in numerous papers by Dr. T. E. Snyder of the 
U. S. Bureau of Entomology, and, thanks to Doctor 
Snyder's work, we are able to give the following account 
of the life of these termites and the history of the de- 
velopment of a fairly complex community from the 
progeny of a single pair of insects. 

The young married couple live amicably together in 
conjugal relations within their narrow cell. The male, 
perhaps, was forced to eject a would-be rival or two, but 
eventually the mouth of the tunnel is permanently sealed, 
and from now on the lives of this pair will be completely 
shut in from the outside world. In due time, a month 
or six weeks after the mating, the female lays her first 
eggs, six or a dozen of them, deposited in a mass on the 
floor of the chamber. About ten days thereafter the 
eggs hatch, and the new home becomes enlivened with a 
brood of little termites. 

The young termites, though active and able to run 
about, are not capable of feeding themselves, and the 
parents are now con fronted, with the task of keeping a 
dozen growing appetites appeased. The feeding formula 



of the termite nursery calls for predigested wood pulp; 
but fortunately this does not have to be supplied from 
outside — the walls of the house furnish an abundance of 
raw material and the digesting is done in the stomachs 
of the parents. The pulp needs then only to be regurgi- 
tated and handed to the infants. This feature in the 
termite economy has a double convenience, for not only 
are the young inexpensively fed, but the gathering of 
the food automatically enlarges the home to accommodate 
the increasing need for space of the growing family. 

That insects should gnaw tunnels through dead wood 
is not surprising; but that they should be able to subsist 
on sawdust is a truly remarkable thing and a dietetic 
feat that few other animals could perform. Dry wood 
consists mostly of a substance called cellulose, which, 
while it is related to the starches and sugars, is a carbo- 
hydrate that is entirely indigestible to ordinary animals, 
though eaten in abundance as a part of all vegetable 
food. The termites, however, are unusually gifted, not 
with a special digestive enzyme, but with minute, one- 
celled, cellulose-digesting protozoan parasites that live 
in their alimentary canals. It is through the agency of 
their intestinal inhabitants, then, that the termites are 
able to live on a diet of dead wood. The young termites 
receive some of the organisms with the food given them 
by their parents and are soon able to be wood eaters 
themselves. Not all termites, however, are known to 
possess these intestinal protozoa, and, as we shall see, 
many of them feed on other things than wood. 

The termite brood thrives upon its wood-pulp diet, 
and by December following the spring in which the young 
were hatched, the members of the new generation begin 
to attain maturity after having progressed through a 
series of moltings, as does any other growing insect. But 
observe, the individuals of this generation, instead of 
developing into replicas of their parents, have taken on 
the form of workers and soldiers ! However, one should 

[ 137] 


never express surprise when dealing with insects; and for 
the present we must accept the strange development 
of the young termites as a matter of tact, and pass on. 

During the middle of winter things remain thus in the 
new family colony. The members of termite species 
that live in the ground, or that pass from wood into the 
ground, probably have tunneled deep into the earth for 

protection from the cold. But in 
February, the mother termite, now 
the queen of the brood, responds 
again to the urge of maternity with 
some more eggs, probably with a 
greater number this time than on 
the first occasion. A month later, 
or during March, the termitary is 
once more enlivened with young 
termites. The king and the queen 
are now, however, relieved of the 
routine of nursery duties by the 
workers of the first brood. The 
latter take over the feeding and 
care of their new brothers and 
sisters, and also do all the excava- 
tion work involved in the enlarging 
of the home. 

In the spring the termites as- 
cend to the surface of the ground 
beneath a board or log, or at the 
base of a stump, and reoccupy 
their former habitation. As the 
galleries are extended, the family 
moves along, slowly migrating thus 
to uneaten parts of the wood and leaving the old tunnels 
behind them mostly packed with excreted wood-pulp and 

When June comes again, the young family may consist 
of several dozen individuals; but all, except the king and 


Fig. 81. A queen of the 
third form, or wingless re- 
productive caste, of Rcti- 
culitermes flampes, (From 
Banks and Snyder) 


queen, are soldiers and workers, the latter much out- 
numbering the former. During the second year, the queen 
lays a still greater number of eggs and probably produces 
them at more frequent intervals. With the increase in 
the activity of her ovaries, her abdomen enlarges and she 
takes on a matronly appearance, attaining a length fully 
twice that of her virgin figure and a girth in proportion. 
The king, however, remains faithful to his spouse; and 
he, too, may fatten up a little, sufficiently to give him 
some distinction amongst his multiplying subjects. The 
termite king is truly a king, in the modern way, for he has 
renounced all authority and responsibility and leads a 
care-free life, observing only the decorums of polite 
society and adhering to the traditions of a gentleman; 
but he also achieves the highest distinction of democracy, 
for he is literally the father of his country. 

Another year rolls by, bringing more eggs, more workers, 
more soldiers. And now, perhaps, other forms appear 
in the maturing broods. These are marked at a certain 
stage of their development by the possession of short 
wing stubs or pads on the back of the normally wing- 
bearing segments. With succeeding molts the wing pads 
become larger and larger, until they finally develop, in 
most of these individuals, into long wings like those of 
the king and the queen when they first flew out from the 
parent colony. At last, then, the new family is to have 
its first swarm; and when the fully-winged members are 
all ready for the event and the proper kind of day arrives, 
the workers open a few exits from the galleries, and the 
winged ones are off. We already know their history, 
for they will only do what their parents did before them 
and what their ancestors have done for millions of gener- 
ations. Let us go back to the galleries. 

A few of the individuals that developed winged pads 
are fated to disappointment, for their wings never grow to 
a functional size and they are thereby prevented from 
joining the swarm. Their reproductive organs and their 



instincts, however, attain maturity, and these short- 
winged individuals, therefore, become males and females 
capable of procreation. They differ from the fully-winged 
sexual forms in a few respects other than the length of the 
wings, and they constitute a true caste of the termite 
community, that of the short-winged males and females 
(Fig. 80). The members of this caste mature along 
with the others, and, Doctor Snyder tells us, many of 
them, regardless of their handicap, actually leave the nest 
at the time the long-winged caste is swarming; as if in 
them, too, the instinct for flight is felt, though the organs 
for accomplishing it are unable to play their part. Just 
what becomes of these unfortunates is a mystery, for 
Doctor Snyder says that after the swarming none of them 
is to be found in the nest. It may be that some of them 
pair and found new colonies after the manner of the 
winged forms, but the facts concerning their history are 
not known. It is at least true that colonies are some- 
times found which have no true royal pair, but in which 
the propagating individuals are members of this short- 
winged reproductive caste. 

Finally, there are also found in the termite colonies 
certain wingless individuals that otherwise resemble the 
winged forms, and which, as the latter, are functionally 
capable of reproduction when mature. These individuals 
constitute a third reproductive caste — the wingless males 
and females. Little is known of the members of this 
caste, but it is surmised that they may leave the nests 
by subterranean passages and found new colonies of their 

Just how long the primary queen of a colony can keep 
on laying eggs is not known, but in the course of years 
she normally comes to the end of her resources, and before 
that time she may be injured or killed through some ac- 
cident. Her death in any case, however, does not mean 
the end of the colony, for the king may provide for the 
continuance of his race, and at the same time console 

[ Ho] 


himself in his bereavement, by the adoption of a whole 
harem of young short-winged females. But if he too 
should be lost, then the workers give the succession to 
one or more pairs of the second- or third-caste repro- 
ductive forms, to whom they grant the royal prerogatives. 
The progeny of any of the fertile castes will include the 
caste of the parents and all castes below them. In other 
words, only winged forms can produce the whole series of 
castes; short-winged parents can not produce long-winged 
offspring; and wingless parents can not produce winged 

Fig. 82. The usual king (A) and queen (B), or winged repro- 
ductive caste after having lost the wings (fig. 79), of Rtticuli- 
termes flavipes. (From Banks and Snyder) 

offspring of any form; but both short-winged and wing- 
less parents can produce soldiers and workers. It ap- 
pears, therefore, that each imperfect fertile insect lacks 
something in its constitution that is necessary for the pro- 
duction of a complete termite individual. 

The production of constitutionally different castes 
from the eggs of a single pair of parents would be a 



highly disconcerting event if it happened anywhere else 
than in a termite colony, where it is the regular thing. 
But the fact of its being regular with termites makes it 
none the less disconcerting to entomologists, for it seems 
to defy the very laws of heredity. 

There can be no doubt of the utility of a caste system 
where the members of each caste know their places and 
their duties, and where nobody ever thinks of starting 
a social revolution. But we should like to know how 
such a svstem was ever established, and how individuals 
of a family are not only born different but are made to 
admit it and to act accordingly. 

These are abstruse questions, and entomologists are 
divided in opinion as to the proper answers. Some have 
maintained that the termite castes are not distinguished 
when the various individuals are young, but are pro- 
duced later by differences in the feeding — in other words, 
it is claimed the castes are made to order by the termites 
themselves. One particular objection to this view is that 
no one has succeeded in finding out what the miraculous 
pabulum may be, and no one has been able to bring about 
a structural change in any termite by controlling its diet. 
On the other hand, it has been shown that in some species 
there are actual differences in the young at the time of 
hatching, and such observations establish the fact that 
insects from eggs laid by one female can, at least, give 
rise to offspring of two or more forms, beside those of 
sex, and that potential differences are determined in the 
eggs. It is most probable that in these forms no struc- 
tural differences could be discovered at an early embryonic 
period, and hence it may be that, where differences are 
not perceptible at the time of hatching, the period of 
differentiation has only been delayed to a later stage of 
growth. It is possible that a solution to the problem of 
the termite castes will be found when a study of the eggs 
themselves has been made. 

We may conclude, therefore, that the structural differ- 

[ H2] 


ences between the termite castes are probably innate, 
and that they arise from differences in the constitutional 
elements of the germ cells that direct the subsequent 
development of the embryos in the eggs and of the young 
after hatching. 

Still, however, there remain questions as to the nature 
of the force that controls termite behavior. Whv do the 
termites remain together in a community instead of 
scattering, each to live its own life as do most other in- 
sects? Why do the workers accept their lot and perform 
all the menial duties assigned to them? Why do the sol- 
diers expose themselves to danger as defenders of the 
nests? Structure can account for the things it is im- 
possible tor an animal to do, but it can not explain positive 
behavior where seemingly the animal makes a choice 
between many lines of possible action open to it. 

In the community of the cells that make up the body 
of an animal, as we learned in Chapter IV, organization 
and control are brought about either through the nerves, 
which transmit an activating or inhibiting force to each 
cell from a central controlling station, or through chemical 
substances thrown into the blood. In the insect com- 
munity, however, there is nothing corresponding to 
either of these regulating influences; nor is there a law- 
making individual or group of individuals as in human 
societies, nor a police force to execute the orders if any 
were issued. It would seem that there must be some 
inscrutable power that maintains law and order in the 
termite galleries. Are we, then, to admit that there is a 
"spirit of the nest," an "dme collective,'' as Maeterlinck 
would have us believe — some pervading force that unites 
the individuals and guides the destinies of the colony 
as a whole? No, scientists can not accept any such idea 
as that, because it assumes that nature's resources are 
no greater than those of man's imagination. Nature is 
always natural, and her ways and means of accomplish- 
ing anything, when once discovered, never invoke things 

[ '43 1 


that the human mind can not grasp, except in their 
ultimate analysis into first principles. Those who have 
faith in the consistency of nature endeavor to push a 
little farther into the great unknown knowable. 

There are a few things known about the termites that 
help to explain some of the apparent mysteries concerning 
them. For example, the members of a colony are for- 
ever licking or nibbling at one another; the workers ap- 
pear to be always cleaning the queen, and they are as- 
siduous in stroking the young. These labial attentions, 
or lip affections, moreover, are not unrewarded, for it 
appears that each member of the colony exudes some 
substance through its skin that is highly agreeable to 
the other members. Furthermore, the termites all feed 
one another with food material ejected from the alimen- 
tary canal, sometimes from one end, sometimes from the 
other. Each individual, therefore, is a triple source of 
nourishment to his fellows — he has to offer exudates 
from the skin, crop food from the mouth, and intestinal 
food from the anus — and this mutual exchange of food 
appears to form the basis for much of the attachment 
that exists among the members of the colony. It accounts 
for the maternal affections, the care of the queen and the 
young by the workers, the brotherly love between the 
workers and the soldiers. The golden rule of the termite 
colony is "feed others as you would be fed by them." 

The termites, therefore, are social creatures because, 
for physical reasons, no individual could live and be 
happy away from his fellows. The same might be said 
of us, though, of course, we like to believe that our social 
instincts have not a purely physical basis. Be that as 
it may, we must recognize that any kind of social tie 
is but one of various possible means by which the benefits 
of community life are insured to the members of the 

The custom of food exchange in the termite colonies 
can not be held to account by any means for all the things 

[ 144] 


that termites do. Where other explanations fail, we have 
always to fall back on "instinct." A true instinct is a 
response bred in the nervous system; and the behavior 
of termites, as of all other insects, is largely brought 

Fig. 83. A fore wing of a termite, Kalotermes approximatus, 

showing the humeral suture (hs) where the wing breaks off when 

it is discarded 

about by automatic reflexes that come into action when 
external and internal conditions are right for their pro- 
duction. The physical qualities of the nervous system 
that make certain reactions automatic and inevitable 
are inherited; they are transmitted from parent to off- 
spring, and bring about all those features of the animal's 
behavior that are repeated from generation to genera- 
tion and which are not to be attributed to the individual's 
response to environmental changes. 

The termites have an ancient lineage, for though no 
traces of their family have been found in the earlier 
records, there can be no doubt that the ancestors of the 
termites were closely related to those of the roaches; and 
the roach family, as we have seen in Chapter III, may be 
reckoned among the very oldest of winged insects. In 
human society it means a great deal to belong to an "old 
family," at least to the members of that family; but in 
biology generally it is the newer forms, the upstarts of 
more recent times, that attain the highest degree of 
organization; and most of the social insects — the ants, 
the bees, and the wasps — belong to families of compara- 
tively recent origin. It is refreshing, therefore, to find 



the belief in aristocracy vindicated by the ancient and 
honorable line of descent represented by the roaches and 
flowering in the termites. 

One particular piece of evidence of the roach ancestry 
of the termites is furnished by the wings. With most 
termites the wings (Fig. 83) are not well developed, and 

Fig. 84. Wings of Mastotermes, the hind wing with a basal 

expansion similar to that of the hind wing of a roach (fig. 53), 

suggesting a relationship between termites and roaches 

their muscles are partly degenerate. In some forms, how- 
ever, the wings (Fig. 84) are distinctly of the roach type 
of structure (Fig. 53), and these forms are undoubtedly 
more closely representative ot the ancestral termites than 
are the species with the usual termite wing structure. 

Our termites and those of other temperate regions con- 
stitute the mere fringes of termite civilization. The ter- 
mites are particularly insects of warm climates, and it is 
in the tropics that they find their most congenial environ- 
ment and attain the full expression of their possibilities. 

In the tropics the characteristic termites are not those 
that inhabit dead wood, but species that construct definite 
and permanent nests, some placed beneath the ground, 



others reared above the surface, and still others built 
against the trunks or branches of trees. Different species 
employ different building materials in the construction 
of their nests. Some use particles of earth, sand grains, 
or clay; others use earth mixed with saliva; still others 
make use of the partly digested wood pulp ejected from 
their bodies; and some use mixed materials. Certain 
kinds of tropical termites, moreover, have foraging habits. 


Fig. 85. Vertical section of an underground nest of an African termite, Termes 
badius. (From Hegh, after Fuller) 

The large central chamber is the principal "fungus garden"; in the wall at the 
left is the royal chamber (re); tunnels lead from the main part of the nest to 
smaller chambers containing fungus, and to the small mounds at the surface 

Great armies of workers of these species leave the nests, 
even in broad daylight, and march in wide columns 
guarded by the soldiers to the foraging grounds, where 
they gather bits of leaves, dead stems, or lichens, and 
return laden with provender for home consumption. 
The underground nests (Fig. 85) consist chiefly of a 



cavity in the earth, perhaps two by three feet in diameter 
and a foot beneath the surface, walled with a thick cement 
lining; but from this chamber there may extend tunnels 
upward to the surface, or horizontally to other smaller 
chambers located at a distance from the central one. 
The termites that live in these nests subsist principally 
upon home-grown food, and it is in the great vaulted 
central chamber that they raise the staple article of their 
diet. The cavity is filled almost entirely with a porous, 
spongy mass of living fungus. The fungi as we ordinarily 
see them are the toadstools and mushrooms, but these 
fungus forms are merely the fruiting bodies sent up from 
a part of the plant concealed beneath the ground or in 
the dead wood; and this hidden part has the form of a 
network, of fine, branching threads, called a mycelium. 
The mycelium lives on decaying wood, and it is the 
mycelial part of the fungus that the termites cultivate. 
They feed on small spore-bearing stalks that sprout from 
the threads of the mycelium. The substratum of the 
termite fungus beds is generally made ot pellets of partly 
digested wood pulp. 

The nests that termites erect above the ground include 
the most remarkable architectural structures produced 
by insects. They are found in South America, Australia, 
and particularly in Africa. In size they vary from mere 
turrets a few inches high to great edifices six, twelve, 
or even twenty feet in altitude. Some are simple mounds 
(Fig. 86 A), or mere hillocks; others have the form of 
towers, obelisks, and pyramids (B); still others look 
like fantastic cathedrals with buttressed walls and taper- 
ing spires (Fig. 87); while lastly, the strangest of all re- 
semble huge toadstools with thick cylindrical stalks and 
broad-brimmed caps (Fig. 86 C). Many of the termites 
that build mound nests are also fungus-growing species, 
and one chamber or several chambers in the nest are 
given over to the fungus culture. 

Termite nests built in trees are usually outlying retreats 



of colonies that live in the ground, for such nests (Fig. 
86 D) are connected with an underground nest by covered 
runways extending down the trunk of the tree. 

The queens of nearly all the termites that live in perma- 
nent nests attain an enormous size by the growth of the 
abdomen, the body becoming thus so huge that the royal 

Fig. 86. Four common types of above-ground nests made by tropical termites 

A, type of small mound nest, varying from a few inches to several feet in height. 

B, type of a large tower or steeple nest, reaching a height of 9 or 10 feet. C, 
a mushroom-shaped nest, made by certain African termites, from 3 to 16 inches 
high. D, a tree nest, showing the covered runway going down to the ground 

female is rendered completely helpless, and must be 
attended in all her wants by the workers. With such 
species the queen is housed in a special royal chamber 
which she never leaves. Her body becomes practically a 
great bag in which the eggs are produced, and so great 
is the fertility of one of these queens that the ripened eggs 
continually issue from her body. It has been estimated 
that in one such species the queen lays four thousand 
eggs a day, and that in another species her daily output 
may be thirty thousand. Ten million eggs a year is pos- 

[ '49] 


Mi^l ^^ 

Fig. 87. Type of pinnacled nest made by species of African termites, some- 
times reaching a height of twenty feet or more 



sibly a world record in ovulation. The royal chamber is 
usually placed near the fungus gardens, and as fast as 
the eggs are delivered by the queen the attendant workers 
carry them off to the garden and distribute them over 
the fungus beds, where the young on hatching can feed 
and grow without further attention. 

From a study of the termites we may draw a few lessons 
for ourselves. In the first place, we see that the social 
form of life is only one of the ways of living; but that, 
wherever it is adopted, it involves an interdependence of 
individuals upon one another. The social or community 
way of living is best promoted by a division of labor among 
groups of individuals, allowing each to specialize and there- 
by to attain proficiency in his particular kind of work. 
The means by which the termites have achieved the bene- 
fits of social life are not the same as those adopted by 
the ants or social bees, and they have little in common 
with the principles of our own social organization. All of 
which goes to show that in the social world, as in the 
physical world, the end alone justifies the means, so far as 
nature is concerned. Justice to the individual is a human 
concept; we strive to equalize the benefits and hardships 
of the social form of life, and in so far as we achieve this 
aim our civilization differs from that of the insects. 



"Plant lice! Ugh," you say, "who wants to read about 
those nasty things! All I want to know is how to get rid 
of them." Yes, but the very fact that those soft green 
bugs that cover your roses, your nasturtiums, your cab- 
bages, and your fruit trees at certain seasons reappear 
so persistently, after you think you have exterminated 
them, shows that they possess some hidden source of 
power; and the secrets of a resourceful enemy are at least 
worth knowing — besides, they may be interesting. 

Really, however, insects are not our enemies; they are 
only living their appointed lives, and it just happens that 
we want to eat some of the same plants that they and their 
ancestors have always fed on. Our trouble with the in- 
sects is just that same old economic conflict that has bred 
the majority of wars; and, in the case between us and the 
insects, it is we who are the aggressors and the enemies of 
the insects. We are the newcomers on the earth, but we 
fume around because we find it already occupied by a host 
of other creatures, and we ask what right have they to be 
here to interfere with us! Insects existed millions of 
years before we attained the human form and aspirations, 
and they have a perfectly legitimate right to everything 
they feed on. Of course, it must be admitted, they do not 
respect the rights of private property; and therein lies 
their hard luck, and ours. 

The plant lice are well known to anyone who has a 
garden, a greenhouse, an orchard, or a field of grain. 
Some call them "green bugs"; entomologists usually call 



them aphids. A single plant louse is an aphis, or an aphid; 
more than one are usually called aphides, or aphids. 

The distinguishing feature of the plant lice, or aphids, 
as we shall by preference call them, is their manner ot feed- 
ing. All the insects described in the preceding chapters 
eat in the usual fashion of biting off pieces of their food, 
chewing them, and swallowing the masticated bits. The 

Fig. 88. Group of green apple aphids feeding along a rib on 
under surface of an apple leaf 

aphids are sucking insects; they feed on the juices of the 
plants they inhabit. Instead ot jaws, they have a piercing 
and sucking beak (Fig. 89), consisting ot an outer sheath 
inclosing four slender, sharp-pointed bristles which can be 
thrust deep into the tissues of a leaf or stem (Fig. 89 B). 
Between the bristles ot the innermost pair (Fig. 90, Mx) 
are two canals. Through one canal, the lower one (h), a 
liquid secretion from glands of the head is injected into the 
plant, perhaps breaking down its tissues; through the 
other (a) the plant sap and probably some of the proto- 
plasmic contents of the plant cells are drawn up into the 
mouth. A sucking apparatus like that of the aphids is 
possessed by all insects related to the aphids, comprising 
the order Hemiptera, and will be more fully described 



in the next chapter, which treats of the cicada, a large 
cousin of the aphids. 

When we observe, now, that different insects feed in 
two quite different ways, some by means of the biting 
type of mouth parts, and others by means of the sucking 
type, it becomes evident that we must know which kind 
of insect we are dealing with in the case of pests we may be 
trying to control. A biting and chewing insect can be 
killed by the mere expedient of putting poison on the out- 
side of its food, if it does not become aware of the poison 
and desist from eating it; but this method would not 
work with the piercing and sucking insects, which extract 
their food from beneath the surface of the plants on 
which they feed. Sucking insects are, therefore, to be 

destroyed by means 
of sprays or dusts 
that will kill them by 
contact with their 
bodies. Aphids are 
usually attacked with 
irritant sprays, and in 
general it is not a 
difficult matter to rid 
infested plants of 
them, though in most 
cases the spraying 
must be repeated 
through the season. 

When any species 
of aphis becomes well 
established on a plant, 
the infested leaves 
(Fig. 88) may be al- 
most as crowded as an 
East Side street on a 
hot summer after- 
noon. But there is 

Fig. 89. The way an aphis feeds on the 

juices of a plant 
A, an aphis with its beak thrust into a rib of a 
leaf. B, section through the midrib of a young 
apple leaf, showing the mouth bristles from the 
beak of an aphis penetrating between the cells 
of the leaf tissue to the vascular bundles, 
while the sheath of the beak is retracted by 
folding back beneath the head 



The green apple aphis {Aphis point) 
A, adult sexual female; B, adult male; C, young female; D, female lay- 
ing an egg; E, eggs, which turn from green to black after they are laid. 
(Enlarged about 20 times) 


no bustle, no commotion, for each insect has its sucking 
bristles buried in the leaf, and its pump is busy keeping 
the stomach supplied with liquid food. The aphis crowds 
are mere herds, not communities or social groups as in 
the case of the termites, ants, or bees. 

Wherever there are aphids there are ants, and in con- 
trast to the aphids, the ants are always rushing about all 
over the place as if they were looking for something and 
each wanted to be the first to find it. Suddenly one spies 
a droplet ol some clear liquid lying on the leaf and gob- 
bles it up, swallowing it so quickly that the spherule 
seems to vanish by magic, and then the ant is off again 
in the same excited manner. The explanation of the 
presence and the actions of the ants among the aphids 
is this: the sap of the plants furnishes an unbalanced diet, 
the sugar content being far too great in proportion to the 
protein. Consequently the aphids eject from their bodies 
drops of sweet liquid, and it is this liquid, called "honey 
dew," that the ants search out so eagerly. Some of the 
ants induce the aphids to give up the honey dew by strok- 
ing the bodies of the latter. The glistening coat often 
seen on the leaves of city shade trees and the shiny liquid 
that bespatters the sidewalks beneath is honey dew dis- 
charged from innumerable aphids infesting the under sur- 
faces of the leaves. 

In studying the termites, we learned that it is possible 
for a single pair of insects to produce regularly several 
kinds of offspring differing in other ways than those of 
sex. In the aphids, a somewhat similar thing occurs in 
that each species may be represented by a number of 
forms; but with the aphids these different forms con- 
stitute successive generations. If events took place in 
a human family as they do in an aphid family, children 
born of normal parents would grow up to be quite different 
from either their father or their mother; the children of 
these children would again be different from their parents 
and also from their grandparents, and when mature they 




perhaps would migrate to some other part of the country; 
here they would have children of their own, and the new 
fourth generation would be unlike any of the three pre- 
ceding; this generation would then produce another, 
again different; and the latter would return to the home 

town of their grandparents 
and great-grandparents, and 
here bring forth children that 
would grow up in the like- 
ness of their great-great- 
great-grandparents! This 
seems like a fantastic tale of 
fiction, too preposterous to 
be taken seriously, but it is a 
commonplace fact among the 
aphids, and the actual gen- 
ealogy may be even more 
complicated than that above 
outlined. Moreover, the 
story is not yet complete, 
for it must be added that all 
the generations of the aphids, 
except one in each series, are 
composed entirely of females 
capable in themselves of re- 
production. In warm " cli- 
mates, it appears, the female 
succession may be uninter- 
How insects do upset our generalizations and our peace 
of mind! We have heard of feminist reformers who would 
abolish men. With patient scorn we have listened to their 
predictions of a millenium where males will be unknown 
and unneeded — and here the insects show us not only that 
the thing is possible but that it is practicable, at least for 
a certain length of time, and that the time can be in- 
definitely extended under favorable conditions. 


Fig. go. Cross-section through 

the base of the beak of an aphis. 

(From Davidson) 

The outer sheath of the beak is the 
labium (Li/)> covered basally by 
the labrum {Lm). The four in- 
closed bristles are the mandibles 
{Md) and the maxillae (Mx) i the 
latter containing between them a 
food canal {a) and a salivary canal 
(b). Only the inner walls of the 
labrum and labium are shown in 
the section 


Since special cases are always more convincing than 
general statements, let us follow the seasonal history of 
some particular aphids, taking as examples the species 
that commonly infest the apple. 

Let the time be a day in the early part of March. 
Probably a raw, gusty wind is blowing from the north- 
west, and only the silver maples with their dark purplish 
clusters of frowzy flowers already open give any sug- 
gestion of the approach of spring. Find an old apple 
tree somewhere that has not been sprayed, the kind of 
tree an entomologist always likes to have around, since 
it is sure to be full of insects. Look closely at the ends 
of some of the twigs and 
you will probably find a 
number of little shiny 
black things stuck close 
to the bark, especially 
about the bases of the 
buds, or tucked under the 
projecting edges of scars 
and tiny crevices (Fig. 
91). Each little speck is 
oval and about one thirty- 
sixth of an inch in length. 

To the touch the ob- 
jects are firm, but elastic, 
and if you puncture one a 
pulpy liquid issues from 
it; or so it appears, at 
least, to the naked eye — ■ 
a microscope would show 
that in this liquid there is 

organization. In short, the tiny capsule contains a young 
aphid, because it is an aphid egg. The egg was de- 
posited on the twig last fall by a female aphis, and its 
living contents have remained alive since then, though 
fully exposed to the inclemencies of winter. 


Fig. 91. Aphis eggs on apple twigs in 
March; an enlarged egg below 


Immediately after being laid in the fall, the germ 
nucleus of the aphis egg begins development, and soon 
forms a band of tissue lying lengthwise on the under sur- 
face of the yolk. Then this scarcely-formed embryo 
undergoes a curious process of revolution in the egg, 
turning on a crosswise axis head foremost into the yolk 
and finally stretching out within the latter with the back 
down and the head toward the original rear end of the 
egg. Thus it remains through the winter. In March 
it again becomes active, reverses itself to its first posi- 
tion, and now completes its development. 

The date of hatching of the apple aphis eggs depends 
much upon the weather and will vary, therefore, ac- 
cording to the season, the elevation, and the latitude; but 
in latitudes from that of Washington north, it is some 
time in April, usually from the first to the third week of 
the month. The eggs of most insects resemble seeds in 

their capacity for lying inert un- 
til proper conditions of warmth 
and moisture bring forth the 
creature biding its time within. 
The eggs of one of the apple 
aphids, however, are killed by 
premature warm weather, or if 
artificially warmed too long be- 
fore the normal time of hatching. 
In general, the final development 
of the aphis embryos keeps pace 
with the development of the 
apple buds, since both are con- 
trolled by the same weather con- 
ditions, and this coordination 
usually insures the young aphids 
against starvation; but the eggs 
commonly hatch a little in ad- 
vance of the opening of the buds, 
and a subsequent spell of cold 

Fig. 92. Eggs of the green 
apple aphis with outer cover- 
ings split before hatching; 
below, an egg removed from 
its covering 



weather may give the young lice a long wait for their 
first meal. 

The approaching time of hatching is signaled in most 

Fig. 93. Hatching of the green apple aphis, Aphis pomi 

A, the egg. B, an egg with the outer coat split. C, the same egg with the 

inner shell split at one end. D-F, three successive stages in the emergence of 

the young insect. G-J, shedding the hatching membrane. K, the empty 

eggshell. L, the young aphid 

J 59l 


cases by the splitting of an outer sheath of the egg (Fig. 
92), exposing the glistening, black, true shell of the egg 
within. Then, from one to several days later, the shell 
itself shows a cleft within the rupture of the outer coat, 
extending along half the length of the exposed egg sur- 
face and down around the forward end (Fig. 93 C). 
From this split emerges the soft head of the young aphis 
(D), bearing a hard, toothed crest, evidently the instru- 
ment by which the leathery shell was broken open, and 
for this reason known as the "egg burster." Once ex- 
posed, the head continues to swell out farther and far- 
ther as if the creature had been compressed within the 
egg. Soon the shoulders appear, and now the young 
aphis begins squirming, bending, inflating its fore parts 
and contracting its rear parts, until it works its body 
mostly out of the egg (E, F) and stands finally upright 
on the tip of its abdomen which is still held in the cleft 
of the shell (G). 

The young aphis at this stage, however, like the young 
roach, is still inclosed in a thin, tight-fitting, membranous 
bag having no pouches for the legs or other members, 
which are all cramped within it. The closely swathed head 
swells and contracts, especially the facial part, and sud- 
denly the top of the bag splits close to the right side of 
the egg burster (Fig. 93 H). The cleft pulls down over 
the head, enlarges to a circle, slides along over the shoul- 
ders, and then slips down the body. As the tightly stretched 
membrane rapidly contracts, the appendages are freed 
and spring out from the body (I). The shrunken pellicle 
is reduced at last to a small goblet supporting the aphid 
upright on its stalk, still held by the tip of the abdomen 
and the hind feet (I). To liberate itself entirely the 
insect must make a few more exertions (J), when, finally, 
it pulls its legs and body from the grip of the drying 
skin, and is at last a free young aphid (L). 

The emergence from the egg and from the hatching 
membrane is a critical period in the life of an aphid. The 

f 160 1 


The rosy apple aphis (Anuraphis roseus) 

A, apple leaves and voung fruit distorted by the aphids; B, under surface 

of an infested leaf; C, immature wingless aphid (greatly enlarged); D, 

immature winged aphis 


process may be completed in a few minutes, or it may 
take as long as half an hour, but if the feeble creature 
should be unable to free itself at last from the drying and 
contracting tissue, it remains a captive struggling in the 
grip of its embryonic vestment until it expires. The 
young aphid successfully delivered takes a few uncertain, 
staggering steps on its weak and colorless legs, and then 
complacently rests awhile; but after about twenty min- 

Fic. 94. Young aphids on apple buds in spring 

utes or half an hour it is able to walk in proper insect 
fashion, and it proceeds upward on its twig, a course 
sure eventually to lead it to a bud. 

While the aphid eggs are hatching, or shortly there- 
alter, the apple buds are opening and unfolding their 
delicate, pale-green leaves, and from everywhere now 
the young aphids come swarming upon them, till the tips 
are often blackened by their numbers (Fig. 94). The 
hungry horde plunges into the hearts of the buds, and 
soon the new leaves are punctured with tiny beaks that 
rob them of their food; and the young foliage, upon which 



the tree depends for a proper start of its spring growth, is 
stunted and yellowed. Now is the time for the orchardist 
to spray if he has not already done so. 

The entomologist, however, takes note that all the 
young aphids on the apple trees are not alike; perhaps 
there are three kinds of them in the orchard (Fig. 95), 
differing slightly, but enough to show that each belongs 
to a separate species. When the first buds infested are 


Fig. 95. Three species of young aphids found on apples in the spring 

A, the apple-grain aphis, Rhopalosiphum prunijoliae. B, the green apple aphis, 

Aphis pomi. C, the rosy apple aphis, Anuraphis roseus 

exhausted, the insects migrate to others, and later they 
spread to the larger leaves, the blossoms, and the young 
fruit. The aphids all grow rapidly, and in the course 
of two or three weeks they reach maturity. 

The full-grown insects of this first generation, those 
produced from the winter eggs, are entirely wingless, and 
they are all females. But this state of affairs in no wise 
hinders the multiplication of the species, for these re- 
markable females are able of themselves to produce off- 
spring (a faculty known as parthenogenesis) , and further- 
more, they do not lay eggs, but give birth to active young. 
Since they are destined to give rise to a long line of sum- 
mer generations, they are known as the stem mothers. 

One of the three aphid species of the apple buds is 
known as the green apple aphis (Pig. 95 B). During the 

[ 162 1 


early part of the season the individuals of this species 
are found particularly on the under surfaces of the apple 
leaves. They cause the infested leaves to curl and to 
become distorted in a characteristic manner (Fig. 96). 
The stem mothers (Fig. 97 A, B) begin giving birth to 
young (C) about twenty-four hours after reaching ma- 
turity, and any one of the mothers, during the course of 
her life of from ten to thirty days, may produce an aver- 
age family of fifty or more daughters, for all her offspring 
are females, too. When 
these daughters grow up, 
however, none of them is 
exactly like their mother. 
They all have one more 
segment in each antenna; 
most of them are wing- 
less (D), but many of 
them have wings — some, 
mere padlike stumps, but 
others well developed or- 
gans capable of flight 
(Fig. 97 E). 

Both the wingless and 
the winged individuals of 
this second generation are 
also parthenogenetic, and 
they give birth to a third 
generation like them- 
selves, including wing- 
less, half-winged, and 
fully-winged forms, but 
with a greater propor- 
tion of the last. From 
now on there follows a 

large number of such generations continuing through the 
season. The winged forms fly from one tree to another, 
or to a distant orchard, and found new colonies. In 


Fig. 96. Leaves of apple infested and 

distorted by the green apple aphis on 

under surfaces 


summer, the green apple aphis is found principally on 
young shoots of the apple twigs, and on water sprouts 
growing in the orchard. 

During the early part of the summer, the rate of pro- 
duction rapidly increases in the aphid colonies, and in- 
dividuals of the summer generations sometimes give 
birth to young a week, after they themselves were born. 
In the fall, however, the period of growth again is length- 
ened, and the families drop offin size; until the last females 
of the season produce each a scant half dozen young, 
though they may live to a much greater age than do the 
summer individuals. 

The young summer aphids born as active insects are 
inclosed at birth in a tight-fitting, seamless, sleeveless, 
and legless tunic, as are those hatched from the winter 
eggs. Thus swathed, each emerges, rear end first, from 
the body of the mother, but is finally held fast by the 
face when it is nearly free. In this position, the em- 
bryonic bag splits over the head and contracts over the 
body of the young aphid to the tip of the abdomen, 
where it remains as a cap of shriveled membrane until 
it finally drops off or is pushed away by the feet. The 
infant, now vigorously kicking, is still held in the ma- 
ternal grasp, and eventually liberates itself only after 
some rather violent struggling; but soon after it is free 
it walks away to find a feeding place among its com- 
panions on the leaf. The mother is but little concerned 
with the birth of her child, and she usually continues 
to feed during its delivery, though she may be somewhat 
annoyed by its kicking. The average summer female 
gives birth to two or three young aphids every day. 

The succession of forms in the families is one of the 
most interesting phases of aphid life. Investigations 
have shown that the winged individuals are produced 
principally by wingless forms, and experiments have 
demonstrated that the occurrence of the winged forms 
is correlated with changes in the temperature, the food 



supply, and the duration ot light. At a temperature 
around sixty-five degrees few winged individuals ever 
appear, but they are produced at temperatures either 
below or above this point. Likewise it has been found 
that when the food supply gives out through the drying 

Fig. 97. The green apple aphis, Aphis pami. A, B, adult stem mothers. 

C, a newly-born young of the summer forms. D, a wingless summer 

form. E, a winged summer form 

of the leaves or by the crowding of the aphids on them, 
winged forms appear, thus making possible a migration 
to fresh feeding grounds. Then, too, certain chemical 
substances, particularly salts of magnesium, added to 
the water or wet sand in which are growing cuttings 
of plants infested with aphids, will cause an increase of 
winged forms in the insects subsequently born. This 
does not happen if the plants are rooted, but it shows 
that a change in the food cmi have an effect on wing 



Finally, it has recently been shown experimentally by 
Dr. A. Franklin Shull that winged and wingless condi- 
tions in the potato aphis may be produced artificially by 
a variation in the relative amount of alternating light 
and darkness the aphids receive during each twenty-four 
hours. Shortening the illumination period to twelve 
hours or less results in a marked increase in the number of 
winged forms born of wingless parents. Continuous 
darkness, however, produces few winged offspring. Maxi- 
mum results perhaps are obtained with eight hours of 
light. The effect of decreased light appears from Doctor 
Shull's experiments to be directly operative on the young 
from thirty-four to sixteen hours before birth, and it is 
not to be attributed to any physiological effect on the 
plant on which the insects are feeding. 

It is evident, therefore, that various unfavorable local 
conditions may give rise to winged individuals in a colony 
of wingless aphids, thus enabling representatives of the 
colony to migrate in the chance of finding a more suit- 
able place for the continuance of their line. The regular 
production of spring and fall migrants is brought about 
possibly by the shorter periods of daylight in the earlier 
and later parts of the season. 

The final chapter of the aphid story opens in the fall 
and, like all last chapters done according to the rules, 
it contains the sequel to the plot and brings everything 
out right in the end. 

All through the spring and summer the aphid colonies 
have consisted exclusively of virgin females, winged and 
wingless, that give birth to virgin females in ever-in- 
creasing numbers. A prosperous, self-supporting femi- 
nist dominion appears to be established. When summer's 
warmth, however, gives way to the chills of autumn, 
when the food supply begins to fail, the birth rate slack- 
ens and falls off steadily, until extermination seems to 
threaten. By the end of September conditions have 
reached a desperate state. October arrives, and the 



surviving virgins give birth in forlorn hope to a brood 
that must be destined for the end. But now, it appears, 
another of those miraculous events that occur so fre- 
quently in the lives of insects has happened here, for the 
members of this new brood are seen at once to be quite 
different creatures from their parents. When they grow 
up, it develops that they constitute a sexual generation, 
composed of females and males! (Plate 2 A, B.) 

Feminism is dethroned. The race is saved. The mar- 
riage instinct now is dominant, and if marital relations 
in this new generation are pretty loose, the time is Octo- 
ber, and there is much to be accomplished before winter 

The sexual females differ from their virgin mothers 
and grandmothers in being of darker green color and in 
having a broadly pear-shaped body, widest near the end 
(Plate 2 A). The males (B) are much smaller than the 
females, their color is yellowish brown or brownish green, 
and they have long spiderlike legs on which they actively 
run about. Neither the males nor the females of the green 
apple aphis have wings. Soon the females begin to pro- 
duce, not active young, but eggs (D). The eggs are de- 
posited most anywhere along the apple twigs, in crevices 
where the bark is rough, and about the bases of the buds. 
The newly-laid eggs are yellowish or greenish (D), but 
they soon turn to green, then to dark green, and finally 
become deep black (E). There are not many of them, 
for each female lays only from one to a dozen; but it 
is these eggs that are to remain on the trees through the 
winter to produce the stem mothers of next spring, who 
will start another cycle of aphid life repeating the his- 
tory of that just closed. 

The production of sexual forms in the fall in temperate 
climates seems to have some immediate connection with 
the lowered temperature, for in the tropics, it is said, 
the aphid succession continues indefinitely through par- 
thenogenetic females, and in most tropical species sexual 



males and females are unknown. In the warmer regions 
of the West Coast of the United States, species that regu- 
larly produce males and females every fall in the East 
continue without a reversion to the sexual forms. 

Of the other two species of apple aphids that infest 

the buds in the spring, one is 
known as the rosy apple aphis 
(Fig. 95 C). The name comes 
from the fact that the early 
summer individuals of this 
species have a waxy pink tint 
more or less spread over the 
ground color of green (Plate 3), 
though many of the adult 
stem mothers (Fig. 98 B) are 
of a deep purplish color. The 
early generations of the rosy 
aphis infest the leaves (Fig. 
98 A, Plate 3 A) and the young 
fruit (Fig. 98 C, Plate 3 A), 
causing the former to curl up 
in tightly rolled spirals, and the 
latter to become dwarfed and 
distorted in form. 

The stem mothers ot the 
rosy aphis give birth partheno- 
genetically to a second gen- 
eration of females which are 
mostly wingless like their moth- 
ers; but in the next generation 
many individuals have wings. 
Several more generations now 
rapidly follow, all females; in 
fact, as with the green aphis, 
no males are produced till late in the season. The winged 
forms, however, appear in increasing numbers, and by 
the first of July almost all the individuals born have wings. 


Fig. 98. The rosy apple 
aphis, Anuraphis roscus 3 on 

A, a cluster of infested and 
distorted leaves. B, an adult 
stem mother. C, young apples 
dwarfed and distorted by the 
feeding of the aphids 


Heretofore, the species has remained on the apple trees, 
but now the winged ones are possessed with a desire for a 
change, a complete change both of scenery and of diet. 
They leave the apples, and when next discovered they are 
found to have established themselves in summer colonies 
on those common weeds known as plantains, and mostly 
on the narrow-leaved variety, the rib-grass, or English 
plantain (Fig. 99). 

As soon as the mi- 
grants land upon the 
plantains they give birth 
to offspring quite unlike 
themselves or any of the 
preceding generations. 
These individuals are of a 
yellowish-green color and 
nearly all of them are 
wingless (Fig. 99). So 
well do they disguise 
their species that ento- 
mologists were a long 
time in discovering their 
identity. Generations of 
wingless yellow females 
now follow upon the 
plantain. But a weed is 
no fit place for the stor- 
age of winter eggs, so, 
with the advent of fall, 
winged forms again ap- 
pear in abundance, and 
these migrate back to the 
apples. The fall mi- 
grants, however, are of two varieties: one is simply a 
winged female like the earlier migrants that came to the 
plantain from the apple, but the other is a winged male 
(Fig. 100 A). Both forms go back to the apple trees, and 


Fig. 99. The rosy apple aphis on nar- 
row-leaved plantain in summer; above, a 
wingless summer form (enlarged) 


there the females give birth to a generation of wingless 
sexual females (B), which, when mature, mate with the 
males and produce the winter eggs. 

The third of the aphid species that infest the spring 
buds of the apple is known as the apple-grain aphis, so 
called because, being a migratory species like the rosy 

Fig. ioo. The winged male (A) and the wingless sexual female (B) of the 
rosy apple aphis 

aphis, it spends the summer upon the leaves of grains 
and grasses. The eggs of the apple-grain aphis are usually 
the first to hatch in the spring, and the young aphids of 
this species (Fig. 95 A) are distinguished by their very 
dark green color, which gives them a blackish appear- 
ance when massed upon the buds. Later they spread 
to the older leaves and to the petals of the apple blossoms, 
but on the whole their damage to the apple trees is less 
than that of either of the other two species. The summer 
history of the apple-grain aphids is similar to that of the 
rosy aphis, excepting that they make their summer home 
on grains and grasses instead of on plantains. In the 
fall, the winged female migrants (Plate 4) come back to 
the apple and there give birth to wingless sexual females, 
which are later sought out by the winged males. 

It would be impossible here even to enumerate the 


^ s 

a a 

g M 

■I -s 



Fig. ioi. Some common aphids of the garden 
A, winged form of the potato aphis, Illinoia solanijolii, one of the largest of 
the garden aphids. B, winged form of the peach aphis, Myzus persicae, 
which infests peach trees and various garden plants. C, wingless form of 
the peach aphis. D, wingless form of the melon aphis, Aphis gossypii. E, 
winged form of the melon aphis 



many species of aphids that infest our common field and 
garden plants (Fig. ioi) and cultivated shrubs and trees, 
to say nothing of those that inhabit the weeds, the wild 
shrubbery, and the forest trees. Almost every natural 
group of plants has its particular kind of aphid, and many 
of them are migratory species like the rosy and grain 
aphis of the apple. There are root-inhabiting species as 
well as those that live on the leaves and stems. The 
Phylloxera, that pest of vineyards in California and 
Prance, is a root aphid. Those cottony masses that 
often appear on the apple twigs in late summer mark 
the presence of the woolly aphis, the individuals of which 
exude a fleecy covering of white waxy threads from their 
backs. The woolly aphis is more common on the roots 
of apple trees, being especially a pest of nursery stock, but 
it migrates to both the twigs and the roots of the apple 
from the elm, which is the home of its winter eggs. 

An underground aphid of particular interest is one that 
lives on the roots of corn. We have seen that all aphids 
are much sought after by ants because of the honey dew 
they excrete, a substance greatly relished and prized by 
the ants. It is said that some ants protect groups of 
aphids on twigs by building earthen sheds over them; but 
the corn-root aphis owes its very existence to the ants. 
A species of ant that makes its nests in cornfields runs 
tunnels from the underground chambers of the nests to 
the bases of nearby cornstalks. In the fall the ants gather 
the winter eggs of the aphids from the corn roots and take 
them into their nests where they are protected from 
freezing during the winter. Then in the spring the ants 
bring the eggs up from the storage cellars and place 
them on the roots of various early weeds. Here the 
stem mothers hatch and give rise to several spring gen- 
erations; but, as the new corn begins to sprout, the ants 
transfer many of the aphids to the corn roots, where 
they live and multiply during the summer and, in the fall, 
give birth to the sexual males and females, which produce 



the winter eggs. The eggs are again collected by the ants 
and carried to safety for the winter into the depths of their 
underground abodes. All this the ants do for the aphids 
in exchange for the honey dew they receive from them. 
The ants have so domesticated these corn-root aphids 
that the aphids would perish without their care. The 
farmer, therefore, who would rid his cornfield of the aphid 
pest, proceeds with extermination measures against the 

The crowded aphid colonies exposed on stems and 
leaves naturally form the happy hunting grounds for a 


Fig. 102. A common ladybird beetle, Coccinella navemnotata, that 

feeds on aphids. (Enlarged 5 times) 

A, the larva. B, the adult beetle 

host of predacious insects. Here are thousands of soft- 
bodied creatures, all herded together, and each tethered 
to one spot bv the bristles of its beak thrust deep into the 
tissues of the plant — a pot-hunter's paradise, truly. 
Consequently, the placid lives of the aphids have many 
interruptions, and vast numbers of the succulent creatures 
serve only as half-way stages in the food cycle of some 
other insect. The aphids have small powers of active 



defense. A pair of slender tubes, the cornicles, projecting 
from the rear end of the body, eject a sticky liquid which 
the aphids are said to smear on the faces of attacking 
insects; but the ruse at best probably does not give much 
protection. Parthenogenesis and large families are the 
principal policies by which the aphids insure their race 
against extinction. 

The presence of "evil" in the world has always been a 
thorn for those who would preserve their faith in the idea 
of beneficence in nature. The irritation, however, is not 

Fig. 103. The aphis-lion, feeding on an aphis held in its jaws 

in the flesh but in a distorted growth of the mind, and 
consequently may be alleviated by a change of mental 
attitude. The thorn itself, however, is real and can not 
be explained away. Beneficence is not a part of the 
scheme by which plants and animals have attained 
through evolution their present conditions and relations. 
On the other hand, there are not good species and bad 
species; for every creature, including ourselves, is a thorn 
to some other, since each attacks a weaker that may 
contribute to its existence. There are many insects that 
destroy the aphids, but these are "enemies" of the aphids 
only in the sense that we are enemies of chickens and of 
cabbages, or of any other thing we kill for food or other 



Recognizing, then, that evil, like everything else, is a 
matter of relativity and depends upon whose standpoint 
it is from which we take our view, it becomes only a par- 
donable bias in a writer if he views the subject from the 
standpoint of the heroes of his story. With this under- 
standing we may note a few of the "enemies" of the 

Everybody knows the "ladybirds," those little oval, 
hard-shelled beetles, usually of a dark red color with 
black spots on their rounded backs (Fig. 102 B). The 
female ladybirds, or better, lady-beetles, lay their orange- 
colored eggs in small groups stuck usually to the under 
surfaces of leaves (Fig. 132 B) and in the neighborhood 
of aphids. When the eggs hatch, they give forth, not 
ornate insects resembling lady-beetles, but blackish little 
beasts with thick bodies and six short legs. The young 
creatures at once seek out the aphids, for aphids are 
their natural food, and begin ruthlessly feeding upon 
them. As the young lady-beetles mature, they grow 
even uglier in form, some of them becoming conspicu- 
ously spiny, but their bodies are variegated with areas of 
brilliant color — red, blue, and yellow — the pattern differ- 
ing according to the species. A common one is shown at 
A of Figure 102. When one of these miniature monsters 
becomes full-grown, it ceases its depredations on the 
aphid flocks, enters a period of quietude, and fixes the 
rear end of its body to a leaf by exuding a glue from the 
extremity of its abdomen. Then it sheds its skin, which 
shrinks down over the body and forms a spiny mat ad- 
hering to the leaf and supporting the former occupant 
by only the tip of the body (Fig. 132 E). With the 
shedding of the skin, the insect has changed from a larva 
to a pupa, and after a short time it will transform into a 
perfect lady-beetle like its father or mother. 

Another little villian, a remarkably good imitation of a 
small dragon (Fig. 103), with long, curved, sicklelike 
jaws extending forward from the head, and a vicious tern- 





perament to match, 
is also a common 
frequenter of the 
aphid colonies and 
levies a toll on the 
lives of the meek 
and helpless insects. 
This marauder is 
well named the 
aphis-lion. He is the larva of a gentle, 
harmless creature with large pale-green 
lacy wings and brilliant golden eyes 
(Fig. 104 A). The parent females 
show a remarkable prescience of the 
nature of their offspring, for they sup- 
port their eggs on the tips of long 
stalks, usu- 
ally attached 
to the under 
surfaces of 
leaves (B). 
The device 
seems to be a 
scheme for preventing the first 
of the greedy brood that will 
hatch from devouring its own 
brothers and sisters still in their 
eggs ; 

Wherever the aphids are 
crowded there is almost sure 
to be seen crawling among 
them soft grayish or green 
wormlike creatures, mostly less 
than a quarter of an inch in 
length. The body is legless and 
tapers to the forward end, 

Fig. 104. The golden- 
eye, Chrysopa, the par- 
ent of the aphis-lion, 

and its eggs 
A, the adult insect. B, 
a group of eggs sup- 
ported on long thread- 
like stalks on the under 
surface of a leaf 

Fig. 105. A larva of a syrphus 
fly feeding on aphids 



which has no distinct head but from which is protruded 
and retracted a pair of strong, dark hooks. Watch one 
of these things as it creeps upon an unsuspecting aphid; 
with a quick movement of the outstretched forward end 
of the body it makes a swing at the fated insect, grabs 
it with the extended hooks, swings it aloft kicking and 
struggling, and relentlessly sucks the juices from its 
body (Fig. 105). Then with a toss it flings the shrunken 
skin aside, and repeats the attack on another aphid. This 
heartless blood-sucker is a maggot, the larva of a fly 
(Fig. 106) belonging to a family called the Syrphidae. 
The adult flies of this family are entirely harmless, though 

Fig. 106. Two common species of syrphus flies whose larvae feed on aphids. 

(Enlarged about j>4 times) 

A, Allograpta obliqua. B, Syrphus americana 

some of them look like bees, but the females of those 
species whose maggots feed on aphids know the habits 
of their offspring and place their eggs on the leaves where 
aphids are feeding. One of them may be seen hovering 
near a well-infested leaf. Suddenly she darts toward 
the leaf and then as quickly is off again; but in the moment 
of passing, an egg has been stuck to the surface right 
in the midst of the feeding insects. Here it hatches 
where the young maggot will find its prey close at hand. 
In addition to these predacious creatures that openly 
and honestly attack their victims and eat them alive, 
the aphids have other enemies with more insidious methods 
of procedure. If you look over the aphid-infested leaves 



Fig. 107. A dead potato 
aphis that has contained a 
parasite, which when adult 
escaped through the door cut 
in the back of the aphis 

home. The guest that so 
ravishes its protector is 
the grub of a small wasp- 
like insect (Fig. 108) with 
a long, sharp ovipositor 
by means ot which it 
thrusts an egg into the 
body of a living aphid 

on almost any plant, you will 
most likely note here and there 
a much swollen aphid of a brown- 
ish color. Closer examination 
reveals that such individuals are 
dead, and many of them have a 
large round hole in the back, 
perhaps with a lid standing up 
from one edge like a trap door 
(Fig. 107). These aphids have 
not died natural deaths; each 
has been made the involuntary 
host ot another insect that con- 
verted its body into a temporary 

Fig. 108. Aphidius, a com- 
mon small wasplike parasite of 

Fig. 109. A female Aphidius inserting an 
egg into the body of a living aphis, where 
the egg hatches; the larva grows to ma- 
turity by feeding in the tissues of the 
aphis. (From Webster) 

(Fig. 109). Here the egg hatches 
and the young grub feeds on 
the juices of the aphid until it 
is itself hill-grown, by which 
time the aphid is exhausted and 
dead. Then the grub slits open 
the lower wall of the hollow 
corpse and spins a web between 
the lips ot the opening and 
against the surface of the leaf 
below, which attaches the aphid 
shell to the support. Thus se- 
cured, the grub proceeds to give 



its gruesome chamber a lining of silk web; which done, it 
lies down to rest and soon changes to a pupa. After a 
short time it again transforms, this time into the adult 
of its species, and the latter cuts with its jaws the hole in 
the back of the aphid and emerges. 

In other cases, the dead aphid does not rest flat on 
the leaf but is elevated on a small mound (Fig. no A). 
Such victims have been inhabited by the grub of a re- 
lated species, which, when full-grown, spins a flat cocoon 
beneath the dead body of its host, and in this inclosure 
undergoes its transformation. The adult insect then 
cuts a door in the side of the cocoon (B), through which 
it makes its exit. 

Insects that usurp the bodies of other insects for their 
own purposes are called parasites. Parasites are the 

Fig. i 10. Aphids parasitized by a parasite that makes a cocoon beneath 

the body of the aphis, where it changes to a pupa and, when adult, 

emerges through a door cut in the side of the cocoon 

worst enemies that insects have to contend against; but 
really they do not contend against them in most cases, 
except in the way characteristic of insects, which is to 
insure themselves against extermination by the number 
of their offspring. The aphid colonies are often, how- 
ever, greatly depleted during a season favorable to the 
predacious and parasitic insects that attack them; but no 
species is ever annihilated by its enemies, for this would 
mean starvation to the next year's brood of the latter. 
The laws of compensation usually maintain a balance 



in nature between the procreative and the destructive 

The insect parasites and predators of other insects in 
general comprise a class of insects that are most beneficial 
to us by reason of their large-scale destruction of species 
injurious to our crops. But, unfortunately, parasites as 
a class do not respect our classification of other creatures 
into harmful and useful species. Even as some predator 
is stalking its prey, another insect is likely to be shadowing 
it, awaiting the chance to inject into its body the egg 
which will mean finally death to the destroyer. Immature 
insects are often found in a sluggish or half-alive condi- 
tion, and an internal examination ot their bodies usually 
reveals that they are occupied by one or more parasitic 
larvae. A larva of any of the lady-beetles, for example, 
is frequently seen attached to a leaf for pupation (Fig. 1 1 1), 
which, instead ot transforming to a pupa, remains inert 
and soon becomes a lifeless form, though still adhering 
to the leaf and bent in the attitude that the pupa would 
assume. In a short time there issues through the dried 
skin a parasite, giving evidence of the fate that has be- 
fallen the unfortunate larva; even it the usurper is not 
seen, the exit hole in the larval skin bears witness to his 
former occupancy and escape. 

And the parasites themselves, do they lead unmolested 
lives? Are they the final arbiters of life and death in the 
insect world? If you are fortunate sometime while study- 
ing aphids out-of-doors, you may see a tiny black mite, 
no bigger than the smallest gnat, hovering about an in- 
fested plant or darting uncertainly from one leaf to 
another, with the air of searching for something but not 
knowing just where to look. You would probably suspect 
the intruder of being a parasite seeking a chance to place 
an egg in the body of an aphid; but here she hovers over 
a group of tat lice without selecting a victim, then per- 
haps alights and runs about on the leaf nervously and 
intensely eager, still finding nothing to her choice. Her 



senses must be dull, indeed, if it is aphids that she wants. 

Do not lose sight of her, however, for her attitude has 

changed; now she certainly has her eye upon something 

that holds her attention, but the object is nothing other 

than one of those swollen parasitized aphids. Yet she 

excitedly runs up to it, feels it, grasps it, mounts upon 

it, examines it all over. Evidently she is satisfied. She 

dismounts, turns about, backs her abdomen against the 

inflated mummy; now 

out comes the swordlike 

ovipositor, and with a 

thrust it is sunken into 

the already parasitized 

aphid. Two minutes 

later her business is 

ended, the ovipositor is 

withdrawn, once more 

sheathed, and the insect 

is off and away. 

This tiny creature is a 
hvperparasite, which is to 
say, a parasite ot a para- 
site. In the act just wit- 
nessed she, too, has thrust 
an egg into the aphid, 
but the grub that will 
hatch from it will devour 
the parasitic occupant 
that is already in pos- 
session of the aphid's 
skin. There are also parasites of hyperparasites, but the 
series does not go on "ad infinitum" as in the old rhyme, 
for the limitation of size must intervene. 

Fie. in. A parasitized Jarva of a lady- 
bird beetle, and one of the parasites 
The larva of the beetle has attached itself 
to a leaf preparatory to pupation, but has 
not changed to a pupa because of the 
parasites within it. Above, one of the 
parasites, which escaped from the beetle 
larva through a hole it cut in the skin of 
the latter 



It is to be observed, in most of our human affairs, that 
we give greatest acclaim to the spectacular, and, further- 
more, that when once a hero has delivered the great thrill, 
all his acts of everyday life acquire headline values. Thus 
a biographer may run on at great length about the petty 
details in the life of some great person, knowing well that 
the public, under the spell of hero worship, will read with 
avidity of things that would make but the dullest plati- 
tudes if told of any undistinguished mortal. Therefore, 
in the following history of our famous insect, universally 
known as the "seventeen-year locust," the writer does not 
hesitate to insert matter that would be dry and tedious 
if given in connection with a commonplace creature. 

Most unfortunate it is, now, that we are compelled to 
divest our hero of his long-worn epithet of "seventeen-year 
locust," and to present him in the disguise of his true 
patronymic, which is cicada (pronounced si-ka'-da). In 
a scientific book, however, we must have full respect for 
the proprieties of nomenclature; and since, as already 
explained in Chapter I, the name "locust" belongs to 
the grasshopper, we can not continue to designate a cicada 
by this term, for so doing would but propagate confusion. 
Moreover, even the praenomen of "seventeen-year" is 
misleading, for some of the members of the species have 
thirteen-year lives. Entomologists, therefore, have re- 
christened the "seventeen-year locust" the periodical 

The cicada family, the Cicadidae, includes many species 



of cicadas in both the New World and the Old, and some 
of them are more familiar, at least by sound, than our 
periodical cicada, because not only are the males noto- 
riously musical, but they are to be heard every year (Fig. 
112). The cicadas of southern Europe were highly es- 
teemed by the ancient Greeks and Romans for their song, 
and they were often kept in cages to furnish entertainment 

Fig. 112. One of the common annual cicadas whose loud song is 
heard every year through the later part of the summer 

with their music. The Greeks called the cicada tettix, 
and Aesop, who always found the weak spot in every- 
body's character, wrote a fable about the tettix and the 
ant, in which the tettix, or cicada, after having sung all 
summer, asked a bite of food from the ant when the chill 
winds of coming winter found him unprovisioned. But 
the practical ant heartlessly replied, "Well, now you can 
dance." This is an unjust piece of satire because the 
moral is drawn to the disparagement of the cicada. 
Human musicians have learned their lesson, however, and 
sign their contracts with the box-office management in 



In the United States there are numerous species of 
"annual" cicadas, so called because they appear every 
year, but their life histories are not actually known in 
most cases. These species are called "locusts," "harvest 
flies," and "dog-day cicadas" (Fig. 112). They are the 
insects that sit in the trees during the latter half of sum- 
mer and make those long shrill sounds that seem to be 
the natural accompaniment of hot weather. Some give 
a rising and falling inflection to their song, which re- 
sembles zwing, zwing, zwing, zwing, (repeated in a long 
series); others make a vibratory rattling sound; and still 
others utter just a continuous whistling buzz. 

During the interval between the times of the appear- 
ance of the adult cicadas, the insects live underground. 
The periodical cicada comprises two races, one of which 
lives in its subterranean abodes for most of seventeen 
years, the other for most of thirteen years. Both races 
inhabit the eastern part of the United States, but the 
longer-lived race is northern, and the other southern, 
though their territories overlap. Most of our familiar in- 
sects complete their life cycle in a single year, and many 
of them produce two or more generations every season. 
For this reason we marvel at the long life of the periodical 
cicada. Yet there are other common insects that normally 
require two or three years to reach maturity, and certain 
beetles have been known to live for twenty years or more 
in an immature stage, though under conditions adverse 
for transforming to the adult. 

Throughout the period of their underground life the 
cicadas have a form quite different from that which they 
take on when they leave the earth to spend a brief period 
in the trees. The form of the young periodical cicada 
at the time it is ready to emerge from the ground is shown 
in Plate 5. It will be seen that it suggests one of those 
familiar shells so often found clinging to the trunk of a 
tree or the side of a post. These shells, in fact, are the 
empty skins of young cicadas that have discarded their 



The mature nymph of the periodical 
cicada in the form in which it leaves the 
ground to transform to the winged adult 
after a subterranean life of nearly 
seventeen years 


earthly form for that of a winged insect of the upper world 
and sunshine, though the skins ordinarily seen are those of 
the annual species. 

The cicada undergoes a striking transformation from 
the young to the adult, but it does so directly and not by 
means of an intervening stage, or pupa. The young of 
an insect that transforms directly is termed a nymph by 
most American entomologists. The last nymphal stage 
is sometimes called a "pupa," but it is not properly so 

The life of the periodical cicada stirs our imagination 
as that of no other insect does. For years we do not see 
the creatures, and then a springtime comes when countless 
thousands of them issue from the earth, undergo their 
transformation, and swarm into the trees. Now, for 
several weeks, the very air seems swayed with the mo- 
notonous rhythm of their song, while the business of ma- 
ting and egg-laying goes rapidly on; and soon the twigs of 
trees and shrubs are everywhere scarred with slits and 
punctures where the eggs have been inserted. In a few 
weeks the noisy multitude is gone, but for the rest of the 
season the trees bear witness to the busy throng that so 
briefly inhabited them by a spotting of their foliage with 
masses of brown and dying leaves where the punctured 
stems have broken in the wind. The young cicadas that 
hatch from the eggs later in the summer silently drop to 
the earth and hastily bury themselves beneath the sur- 
face. Here they live in solitude, seldom observed by 
creatures of the upper world, through the long period of 
their adolescent years, only to enjoy at the end a few 
brief weeks of life in the open air in the fellowship of 
their kind. 

The Nymphs 

Of the underground life of the periodical cicada we 
still know very little. The fullest account of the history 
of this species is that given by Dr. C. L. Marlatt in his 



Bulletin, The Periodical Cicada, published by the United 
States Bureau of Entomology in 1907. Doctor Marlatt 
describes six immature stages of the periodical cicada 
between the egg and the adult. 

The young cicada that first enters the ground is a 
minute, soft-bodied, pale-skinned creature about a twelfth 
of an inch in length (Fig. 126). The body is cylindrical 
and is supported on two pairs of legs, the front legs being 
the digging organs; the somewhat elongate head bears a 
pair of small dark eyes and two slender, jointed antennae. 
At no stage has the cicada jaws like those of the grass- 
hopper; it is a sucking insect, related to the aphids, and 
is provided with a beak arising from the under surface 
of the head, but when not in use the beak is turned back- 
ward between the bases of the front legs. Throughout 
the period of its underground life, the cicada subsists 
on the sap of roots. 

During more than a year the young cicada retains ap- 
proximately the form it has at hatching, though the body 
changes somewhat in shape, principally by an increase 
in the size of the abdomen (Fig. 113). According to 
Doctor Marlatt, a nymph of the seventeen-year race first 

sheds its skin, or molts, some- 
time during the first two or 
three months of the second 
year of its life. 

In its second stage it be- 
comes a little larger and is 
marked by a change in the 
structure of the front legs, 
the terminal foot part of 
each being reduced to a 
mere spur and the fourth 
section being developed into 
a strong, sharp-pointed pick which forms a more efficient 
organ for digging. The second stage lasts nearly two 
years; then the creature molts again and enters its third 

I 186 I 

Fig. 113. Nymph of the periodi- 
cal cicada in the first stage, about 
18 months old, enlarged 15 times. 
(From Marlatt) 


Fig. i 14. Nymph of the periodical 
cicada in the fourth stage, about 12 years 
old, enlarged 1}i times. (From Marlatt) 

stage, which is about a year in length. In the fourth 
stage, which lasts perhaps three or four years, the nymph 
(Fig. 114) shows distinct wing pads on the two wing- 
bearing segments of the 
thorax. In the fifth stage 
the insect, sometimes now 
called a "pupa," takes on 
the form it has when it 
finally emerges from the 
earth; its front feet are 
restored and its wing 
pads are well developed, 
but it has entirely lost its 
small nymphal eyes. 
Once more, before its 
long underground sen- 
tence is up, the nymph molts, and enters the sixth and 
last stage of its subterranean life. When mature (Plate 5) 
it is about an inch and a quarter in length, thick-bodied, 
and brown in color; it appears to have a pair of bright-red 
eyes on the head, but these are the eyes of the adult 
inside showing through the nymphal skin. 

According to the investigations of Doctor Marlatt, the 
nymphs of the periodical cicada do not ordinarily burrow 
into the earth below two feet, and most of them are to be 
found at depths varying from eight to eighteen inches. 
However, there are reports of their having been discovered 
ten feet beneath the surface, and they have been known 
to emerge from the floors of cellars at the time of trans- 
formation to the adult stage. There is no evidence that 
the insects, even when present in great numbers in the 
earth, do any appreciable damage to the vegetation on 
the roots of which they feed. 

Some time before the mature nymphs emerge from the 
ground, probably in April of the last year of their lives, 
the insects come up from their subterranean burrows and 
construct a chamber of varying depth just below the 



115. Outlines of plaster casts of underground resting chambers of the 
mature nymph of the periodical cicada (about one-half natural size) 

[ 188 


surface. A good idea of the size and shape of these cham- 
bers may be obtained by filling the opened holes with a 
mixture of plaster of Paris in water, letting the plaster 
harden, and then digging up the casts. Figure 115 shows 
casts of a number of chambers made in this way. Some, it 
is seen, are mere cups about an inch in depth, but most of 
them are long and narrow, descending several inches into 
the ground, the longest being six inches or more in depth. 
The width is usually about five-eighths of an inch. All 
the chambers have a distinct enlargement at the bottom, 
and most of them are slightly widened at the top. The 
upper wall of each is separated from the surface by a 
layer of undisturbed soil about half an inch in thick- 
ness, which is not broken until the insect is ready to 

The shafts are seldom straight, their courses being 
more or less tortuous and inclined to the surface, as the 
miner had to avoid roots and stones obstructing the 
vertical path. The interior contains no debris of any 
kind, and the walls are smooth and compact. Below 
each chamber there is always evidence of a narrower 
burrow going irregularly downward into the earth, but 
this tunnel is filled to the chamber floor with black granu- 
lar earth. The burrows examined by the writer near 
Washington in 19 19 were dug through compact red clay, 
and the lower tunnels here made a distinct black path 
through the red of the surrounding clay, where some 
could be followed for a considerable distance. The black 
color of the earth filling the tunnels was possibly due to 
an admixture of fecal matter. 

The chambers, as we have noted, are closed at the top 
until the cicada is ready to emerge. The largest chambers 
are many times the bulk of the nymph in volume, and it 
becomes, then, a question as to what the insect does with 
the material it removed in making a hole of such size. It 
seems improbable that it could have been carried down 
into the lower tunnel, for this would be filled with its own 



debris. The insects themselves will give an answer to 
the question if several of them are placed in glass tubes 
and covered with earth; but, to understand the cicada's 
technique, we must first study the mechanism of its 
digging tools, the front legs. 

The front leg of a mature cicada nymph (Fig. 116 A) is 

composed of the same 
parts as any other of its 
legs. The third segment 
from the base, which is 
the femur (F), is large 
and swollen, and has a 
pair of strong spines and 
a comb of smaller ones 
projecting from its lower 
edge. The next segment 
is the tibia {Tb). It is 
curved and terminates 
in a strong recurved 
point (B). Finally, at- 
tached to the inner sur- 
face of the tibia, well up 
from its terminal point, 
is the slender tarsus 
{Tar). The tarsus can 
be extended beyond the 
tibial point when the insect is walking or climbing, but 
can also be turned inward at a right angle to the latter, 
as shown at B, or bent back against the inner surface of 
the tibia. 

Let us now return to the insects in the earth-filled 
tubes, where they are industriously at work. It will be 
seen that they are using the curved, sharp-pointed tibiae 
as picks with which to loosen the earth, the tarsi being 
turned back and out of the way. The two legs, working 
alternately, soon accumulate a small mass of loosened 
material in front of the insect's body. Now there is a 

[ 19°] 

Fig. 116. The digging organ, or front 

leg, of the mature cicada nymph 
A, right leg, inner surface (4 times natural 
size). B, the tarsus {Tar) bent inward at 
right angles to the tibia (7^), the posi- 
tion in which it is used as a rake 
Cx, basal joint or coxa; Xr, trochanter; F } 
femur; Tb, tibia; Tar, tarsus, with two 
terminal claws 


cessation ot digging and the tarsi are turned forward at 
right angles to the tibiae to serve as rakes (Fig. 1 1 6 B). 
The mass of earth pellets is scraped in toward the body, 
and — here comes the important part, the cicada's special 
technique — the little pile of rakings is grasped by one 
front leg between the tibia and the femur (Fig. 116 A, 
Tb and F), the former closing up against the spiny margin 
of the latter, the leg strikes forcibly outward, and the 
mass of loosened earth is pushed back into the surrounding 
earth. The process is repeated, first with one leg, then 
with the other. The miner looks like a pugilist training 
on a punching bag. Now and then the worker stops and 
rubs his legs over the protruding front of the head to 
clean them on the rows of bristles which cover each side 
of the face. Then he proceeds again, clawing, raking, 
gathering up the loosened particles, thrusting them back 
into the wall of the growing chamber. His back is firmly 
pressed against the opposite side of the cavity, the middle 
legs are bent forward until their knees are almost against 
the bases of the front legs, their tibiae lying along the wing 
pads. The hind legs keep a normal position, though 
held close against the sides of the body. 

From what we know of the cicada's spring habits 
underground, we can infer that the nymphs construct 
their chambers on their arrival near the surface during 
April, and that, when the chambers are completed, the 
insects wait within for the signal to emerge and trans- 
form into the adult. Then they break through the thin 
caps at the surface and come out. It would be difficult 
to explain how thev know when they are so near the top 
of the ground, and why some construct ample chambers 
several inches deep while others make mere cells scarcely 
larger than their bodies. Do they burrow upward till the 
pressure tells them that the surface is only a quarter of 
an inch or so away, and then widen the debris-filled 
tunnel downward? Evidently not, because the chamber 
walls are made of clean, compacted clay in which there 



is no admixture of the blackened contents of the burrows. 
It is unlikely, too, that they base their judgments on a 
sense of temperature, because their acts are not regulated 
by the nature of the season, which, if early or late, would 
fool them in their calculations. 

Early in the spring, before the proper emergence season, 
cicada nymphs are often found beneath logs and stones. 
This is to be expected, for, to the ascending insect, some- 
thing impenetrable has blocked the way, and there is 
nothing to tell it that it has already reached the level of 
the surface. 
A more curious thing, often observed in some localities, 

is that the insects some- 
times continue their 
chambers up above the 
surface of the ground 
within closed turrets of 
mud from two to several 
inches in height (Fig. 
117). At certain places 
these cicada "huts" have 
been reported as occur- 
ring in great numbers; 
and it has been supposed 
that they may be built 
wherever there is some- 
thing about the nature of 
the soil that the insects 
do not like, the earth 
being perhaps too damp, 
for they are frequently 
found where the ground 
is unusually wet. On the other hand, the turrets have 
been observed in dry situations as well, and towers and 
holes flush with the surface frequently occur intermingled. 
The writer has had no opportunity of studying the cicada 
turrets, but a most interesting description of them is given 

[ 19*1 

Fig. 117. Earthen turrets sometimes, 
erected by the nymphs of the periodical 
cicada as continuations from their under- 
ground chambers. One cut open showing 
the tubular cavity within. (From photo- 
graph by Marlatt) 


The cicada just after emergence from the nymphal 
skin. (Enlarged two-thirds) 


by Dr. J. A. Lintner in his Twelfth Report on the bisects of 
New York, published in 1897. Dr. Lintner says the 
turrets are constructed by the nymphs with soft pellets 
of clay or mud brought up from below and firmly pressed 
into place, and he records an observation on a nymph 
caught at work with a pellet of mud in its claws. We 
mav infer, then, that the cicada's style of work as a 
mason is only a modification of its working methods as a 
miner, but it appears that no one has yet actually watched 
the construction of one of the turrets. At emergence 
time the towers are opened at the top and the insects come 
forth as they would from an ordinary chamber beneath the 
level of the ground. 

The Transformation 

The period of emergence for most of the cicadas of the 
northern, or seventeen-year, race is the latter part of 
May. The time of their appearance over large areas is 
much more nearlv uniform than with most other insects, 
which show a wide variation according to temperature as 
determined bv the season, the elevation, and the latitude. 
Nevertheless, observations in different localities show 
that the cicada, too, is influenced by these conditions. 
In the South, members of the thirteen-year race may 
emerge even a month earlier, the first individuals of the 
southernmost broods appearing in the latter part of 

By some feeling of impending change the mature 
nymph, waiting in its chamber, knows when the time of 
transformation is at hand. Somehow nature regulates 
the event so that it will happen in the evening, but, once 
the hour has come, no time is to be lost. The nymph 
must break out of its cell, find a suitable molting site 
and one in accord with the traditions of its race, and there 
fix itself by a firm grip of the tarsal claws. At the be- 
ginning of the principal emergence period large numbers 
of the insects come out of their chambers as early as 

[ 193 1 


five o'clock in the afternoon; but after the rush of the 
first few days not many appear before dusk. 

It is difficult to catch a nymph in the very act of making 
its exit from the ground, and apparently no observations 
have been recorded on the manner of its leaving. Do the 
insects leisurely open their doors some time in advance 
of their actual need and wait below till the proper hour, 
or do they break through the thin caps of earth and emerge 
at once? Digging up many open chambers revealed a 
living nymph in only one. Another issued from one of 
several dozen holes filled with liquid plaster for obtaining 
casts. Add to this the fact that great numbers of fresh 
holes are to be seen every morning during the emergence 
season, and the evidence would appear to indicate that 
the insects open their doors in the evening and come out 
at once. Only one chamber was found in the daytime 
partly opened. 

It the insects are elusive and wary of being spied 
upon as they make their debut into the upper world, a 
witness of their subsequent behavior does not embarrass 
them at all. However, events are imminent; there is 
no time to waste. The crawling insects head for anv 
upright object within their range of vision — a tree is the 
ideal goal if it can be attained, and since the creatures 
were born in trees there is likely to be one near by. Yet 
it frequently happens that trees in which many were 
hatched have been since cut down, in which case the 
returning pilgrims must make a longer journey perhaps 
than anticipated. But the transformation can not be 
delayed; if a tree is not accessible, a bush or a weed, a 
post, a telegraph pole, or a blade of grass will do. On 
the trees some get only so tar as the trunk, others attain 
the branches, but the mob gets out, upon the leaves. 
Though thousands emerge almost simultaneously, they 
have not all been timed alike. Some have but a few 
minutes to spare, others can travel about for an hour or 
so before anything happens. 



The external phase of transformation, more strictly 
the shedding of the last nymphal skin, has been many 
times observed. It is nothing more than what all insects 
do. But the cicada is notorious because it does the thing 
in such a spectacular way, almost courting publicity 
where most insects are shy and retiring. As a conse- 
quence the cicada is famous; the others are known only 
to prying entomologists. 

Let us suppose now that our crawling nymph has 
reached a place that suits it, say on the trunk of a tree, 
or better still on a piece of branch provided for it and 
taken into a lighted room where its doings can be more 
clearly observed. Though the insects choose the evening 
for emergence, they are not bashful at all about changing 
their clothes in the glare of artificial light. The progress 
of this performance is illustrated by Figure 118. The 
first drawing shows the nymph still creeping upward; 
but in the next (2) it has come to rest and is cleaning 
its front feet and claws on the brushes of its face, just 
as did those confined to the glass tubes to give a demon- 
stration of their digging methods. The front feet done, 
the hind ones are next attended to. First one and then 
the other is slowly flexed and then straightened back- 
ward (j>) while the foot scrapes over the side of the ab- 
domen. Several times these acts are repeated calmly 
and deliberately, for it is an important thing that the 
claws be well freed from any particles of dry earth that 
might impair their grip on the support. At last the 
toilet is completed, though the middle feet are always 
neglected, and the insect feels about on the twig, grasp- 
ing now here, now there, till its claws take a firm hold 
on the bark. At the same time it sways the body gently 
from side to side as if trying to settle comfortably for the 
next act. 

Thirty-five minutes may be consumed in the above 
preliminaries and there is next a ten-minute interval of 
quietude before the real show begins. Then suddenly 



Fig. i i 8. Transformation of the periodical cicada from the mature 
nymph to the adult 

[i 9 6] 


the insect humps its back (,/), the skin splits along the 
midline of the thorax (5), the rupture extending forward 
over the top of the head and rearward into the first seg- 
ment of the abdomen. A creamy white back, stamped 
with two large jet-black spots, now bulges out ((5, 7); 
next comes a head with two brilliant red eyes (8); this is 
followed by the front part of a body (9) which bends 
backward and pulls out legs and bases of wings. Soon 
one leg is free (/o), then four legs (//), while four long, 
glistening white threads pull out of the body of the issuing 
creature but remain attached to the empty shell. These 
are the linings of the thoracic air tubes being shed with 
the nymphal skin. Xow the bodv hangs back down, 
when all the legs come free (12), and now it sags peril- 
ously (/j) as the wings begin to expand and visibly 

Here another rest intervenes; perhaps twentv-five min- 
utes may elapse, while the soft new creature, like an in- 
verted gargoyle supported only by the rear end of its 
body, hangs motionless far out from the split in the back 
of the shell. Now we understand why the nymph took 
such pains to get a firm anchorage, for, should the dead 
claws give way at this critical stage, the resulting fall 
most probably would prove fatal. 

The next act begins abruptly. The gargoyle moves 
again, bends its body upward (/</), grasps the head and 
shoulders of the slough (/j), and pulls the rear parts 
of its body free from the gaping skin {16). The body 
straightens and hangs downward (//). At last we be- 
hold the free imago, not yet mature but rapidly assum- 
ing the characters of an adult cicada. The new creature 
hangs for a while from the discarded shell-like skin, 
clinging by the front and middle legs, sometimes by the 
first alone; the hind ones spread out sideways or bend 
against the body, rarely grasping the skin. The wings 
continue to unfold and lengthen, finally hang flat, fully 
formed, but soft and white (iS). Here the creature 

[ J 97] 


usually becomes restless, leaves the empty skin (/<?), and 
takes up a new position several inches away (20). 

At this stage the cicada is strangely beautiful. Its 
creamy-yellow paleness, intensified by the great black 
patches just behind the head and relieved by the pearly 
flesh tint of the mesothoracic shield, its shining red eyes, 
and the milky, semitransparent wings with deep chrome 
on their bases make a unique impression on the mind. 
There is a look of unreality about the thing, which out of 
doors (Plate 6) becomes a ghostlike vision against the 
night. But, even as we watch, the color changes; the 
unearthly paleness is suffused with bluish gray, which 
deepens to blackish gray; the wings flutter, fold against 
the back, and the spell is broken — an insect sits in the 
place of the vanished specter. 

The rest is commonplace. The colors deepen, the grays 
become blackish and then black, and after a few hours the 
creature has all the characters of a fully matured cicada. 
Early the next morning it is fluttering about, restless to 
be off with its mates to the woods. 

The time consumed by the entire performance, from 
the splitting of the skin (Fig. 118,5) to the folding of the 
wings above the back {21), varies with different indi- 
viduals, observed at the same time and under the same 
conditions, from forty-five minutes to one hour and 
twelve minutes. Most of the insects have issued from 
the nymphal skins before eleven o'clock at night, but oc- 
casionally a straggler may be seen in the last act as late 
as nine o'clock the following morning — probably a be- 
lated arrival who overslept the night before. 

Thus, to the eye, the burrowing and crawling creature 
of the earth becomes transfigured to a creature of the air; 
yet the visible change is mostly but the final escape of 
the mature insect from the skin of its preceding stage. 
Aside from a few last adjustments and the expansion of the 
wings, the real change has been in progress within the 
nymphal skin perhaps for years. We do not truly witness 




the transformation; we see only the throwing off of the 
shell that concealed it, as the circus performer strips off 
the costume of the clown and appears already dressed 
in that of the accomplished acrobat. 

The Adults 

The adult cicada bears the stamp of individuality. In 
form he does not closely resemble any oi our everyday 
insects, and he has a personality all his own; he impresses 
us as a "distinguished foreigner in our midst." The body 
of the periodical cicada is thick-set (Fig. 119), the face is 
bulging, the forehead is wide, with the eyes set out promi- 
nently on each side; from the under side of the head the 
short, strong beak projects downward and backward be- 
tween the bases of the front legs. The colors are dis- 
tinctive but not striking. The back is plain black (Plate 
7); the eyes are bright red; the wings are shiny transparent 
amber with strongly marked orange-red veins; the legs 
and beak are reddish, and there are bands of the same 
color on the rings of the abdomen. Each front wing is 
branded near the tip with a conspicuous dark-brown W. 

With both the seventeen-year race and the thirteen- 
year race of the periodical cicada there is associated a 
small cicada, which, however, differs so little except in 
size from the others (Fig. 119) that entomologists gener- 
ally regard it as a mere variety of the larger form, the 
latter always including by far the greater number of 
individuals in any brood. 

The male cicada has a pair of large drumheads beneath 
the bases of the wings on the front end of the abdomen 
(Fig. 120, Tm). These are the instruments by which 
he produces his music, and we will give them more atten- 
tion presently. The female cicada has no drums nor other 
sound-making organs; she is voiceless, and must keep 
silence no matter how much her noisy mate may disturb 
her peace. The chief distinction of the female is her 
ovipositor, a long, swordlike instrument used for inserting 

[ '99 1 


Fig. 119. Males of the large and small form 
of the periodical cicada (natural size) 

the eggs into the twigs of trees and bushes. Ordinarily the 
ovipositor is kept in a sheath beneath the rear half of the 
abdomen, but when in use it can be turned downward 
and forward by a hinge at its base (Plate 7). The oviposi- 
tor consists of two 
lateral blades, and a 
guide-rail above. The 
blades excavate a cav- 
ity in the wood in- 
to which the eggs 
are passed through 
the space between the 

It was formerly sup- 
posed that the period- 
ical cicada takes no 
food during the brief 
time of its adult life, 
but we know from the 
observations of Mr. \Y. T. Davis, Dr. A. L. (Juaintance, 
and others and from a study of the stomach contents made 
by the writer that the insects do feed abundantly by 
sucking the sap from the trees on which they live. The 
cicada, being a 
near relative of 
the aphids, has 
also, as we have 
already noted, a 
piercing and suck- 
ing beak by which 
it punctures the 
plant tissues and 
draws the sap up 
to its mouth. Un- 
like the other 

SUCkillS? insects ^ IG ' I2 °' ^ male of the periodical cicada with the 

1 ■ «■ wings spread, showing the ribbed sound-producing 

that infest plants, organs, or tympana (Tm), on the base of the abdomen 



however, the cicadas cause no visible damage to the trees 
by their feeding. Perhaps this is because their attack 
lasts such a short time and comes at a season when the 
trees are at their fullest vigor. 

The details of the head structure of the cicada and 
the exposed part of the beak are shown in Figure 121, 
which gives in side view the head ot a fully matured 
adult, detached from the body by the torn neck mem- 
brane (XMb), with the beak (Bk) extending downward 
and backward below. The large eyes (E) project from 
the sides ot the upper part of the head. The face is 
covered by a large protruding, striated plate (Clp). The 
cheek regions are formed by a long plate (Ge) on each side 
below the eyes; and between each cheek plate and the 
striated facial plate is partlv concealed a narrower plate 
(Md). The cicada has no jaws. Its true mouth is shut 
in between the large flap (AClp), below the striated facial 
plate, and the base ot the beak. 

If the outer parts of the head about the mouth can be 
separated, there will be seen within them some other very 
important parts ordinarily hidden from view. In a 
specimen that has been killed in the act of emerging from 
the nymphal skin, when it is still soft, the outer parts are 
easily separated, exposing the structures shown at B of 
the same figure. 

It is now to be seen (Fig. 121 B) that the beak con- 
sists of a long troughlike appendage (Lb) suspended from 
beneath the back part of the head, having a deep groove 
on its front surface in which are normally ensheathed 
two pairs of slender bristles (MdB, MxB), of which only 
the two of the left side are shown in the figure. In front 
of the bases of the bristles there is exposed a large tongue- 
like organ which is the hvpopharynx (Hphy). Between 
this tongue and the flap hanging from the front of the 
face is the wide-open mouth (Mf/i), the roof of which (if) 
bulges downward and almost fills the mouth cavity. 
The way in which the cicada obtains its liquid food de- 



pends upon the finer structure and the mechanism of 
the parts before us. 

Each one of the second pair of bristles has a furrow 
along the entire length of its inner surface, and the two 

Fig. 121. The structure of the head and sucking beak of the adult cicada 

A, the head in side view with the beak (Bk) in natural position 

B, the head of an immature adult: the mouth (Mth) opened, exposing the roof 
(e) of the sucking pump (see fig. 1 22), and the tonguelike hypopharynx (Hphy) ; 
the parts of the beak separated, showing that it is composed of the labium 
(IJ>), inclosing normally two pairs of long slender bristles (MdB, MxB, only 

one of each pair shown) 
a, bridge between base of mandibular plate (Md) and hypopharynx (Hphy); 
Aclp, anteclypeus; Ant, antenna; Bk, beak; Clp, clypeus; e, roof of mouth cavity, 
or sucking pump; Ge, gena (cheek plate); Hphy, hypopharynx; Lb, labium; Lm, 
labrum; Md, base of mandible; MdB, mandibular bristle; Mth, mouth; Mx, 
maxilla; MxB, maxillary bristle; NMb, neck membrane; O, ocelli 

bristles, small as they are, are fastened together by inter- 
locking ridges and grooves, so that their apposed fur- 
rows are converted into a single tubular channel. In 
the natural position, these second bristles lie in the 
sheath of the beak (Fig. 121 A) between the somewhat 
larger first bristles. Their bases separate at the tip J of 

[ 202 ] 


the tongue (Hphv) to pass to either side of the latter 
organ, but the channel between them here becomes con- 
tinuous with a groove on the middle of the forward sur- 
face of the tongue. When the mouth-opening is closed, 
as it always is in the fully matured insect, the tongue 
groove is converted into a tube which leads upward from 
the channel between the second bristles into the inner 
cavity of the mouth. It is through this minute passage 
that the cicada obtains its liquid food; but obviously 
there must be a pumping apparatus to furnish the sucking 

The sucking mechanism is the mouth cavity and its 
muscles. The mouth cavity, as seen in a section of the 
head (Fig. 122, Pmp), is a long, oval, thick-walled capsule 
having its roof, or anterior wall (e), ordinarily bent inward 
so far as almost to fill the cavity. Upon the midline 
of the roof is inserted a great mass of muscle fibers 
{PmpMcls) that have their other attachment on the 
striated plate of the face (C/p). The contraction of these 
muscles lifts the roof, and the vacuum thus created in 
the cavity of the mouth sucks up the liquid food. Then 
the muscles relax, and the elastic roof again collapses, 
but the lower end comes down first and forces the liquid 
upward through the rear exit of the mouth cavity into 
the pharynx, a small muscular-walled sac (Phy) lying 
in the back of the head. From the pharynx, the food 
is driven into the tubular gullet, or oesophagus (OE), 
and so on into the stomach. 

The bases of both pairs of bristles are retracted into 
pouches of the lower head wall behind the tongue, and 
upon each bristle base are inserted sets of protractor 
and retractor muscle fibers. By means of these muscles, 
the bristles can be thrust out from the tip of the beak or 
withdrawn, and the bristles of the stronger first pair 
are probably the chief organs with which the insect 
punctures the tissues of the plant on which it feeds. As 
the bristles enter the wood, the sheath of the beak can 



be retracted into the flexible membrane of the neck at 
its base. 

One other structure ot interest in the cicada's head 
should be observed. This is a force pump connected 
with the duct (Fig. 122, SalD) of the large salivary glands 
{Gl, Gl) and used probably tor injecting into the wound 
of the plant a secretion which perhaps softens the tissues 
of the latter as the bristles are inserted. Possibly the 

saliva has also a 
digestive action 
on the food liquid. 
The salivary 
pump (SalPmp) 
lies behind the 
mouth, and its 
duct opens on the 
extreme tip of the 
tongue, where the 
saliva c a n b e 
driven into the 
channel of the 
second bristles. 
Most sucking in- 
sects have two 
parallel channels 
between these 
bristles (Fig. 90), 
one for taking 
food, the other 
for ejecting saliva, 
and the cicada 
probably has two 
also, though in- 
vestigators differ 
as to whether 
there are two or 
only one. 


Fig. 122. Median section of the head and beak of 

an adult cicada 
The sucking pump (Pmp) is the mouth cavity, the 
collapsed roof of which (e) can be lifted like a piston 
by the large muscles (PmpMcls) arising on the 
clypeus (C/p). The liquid food ascends through a 
channel between the maxillary bristles (MxB), is 
drawn into the mouth opening (A/M), and pumped 
back into the pharynx {Pky)> from which it goes into 
the oesophagus (OE). A salivary pump (Sa/Pmp) 
opens at the tip of the hypopharynx (Hphy) y dis- 
charging the secretion of the large glands (G/, Gl) 

into the beak 



The head ot the cicada is thus seen to be a wonderful 
mechanism tor enabling the insect to feed on plant sap. 
The piercing beak and the sucking apparatus, however, 
are characters distinguishing the members of a whole 
order of insects, the Hemiptera, or Rhynchota. This 
order includes, besides the cicadas, such familiar insects 
as the plant lice, the scale insects, the squash bugs, 
the giant water bugs, the water striders, and the bed 
bugs. To the sucking insects properly belongs the name 
"bug," which is not a synonym of "insect." 

It is believed, of course, that the parts of the sucking 
beak of a hemipteran insect correspond with the mouth 
parts of a biting insect, described in Chapter IV (Fig. 
66), but it has been a difficult matter to determine the 
identities of the parts in the two cases. Probably the 
anterior narrow plate on the side of the cicada's head 
(Fig. 121, Md) is a rudiment of the base of the true jaw, 
or mandible. The first bristles (MdB) are outgrowths 
of the mandibular plates, which have become detached 
from them and made independently movable by special 
sets of muscles. The second bristles (MxB) are out- 
growths of the maxillae, which are otherwise reduced 
to small lobes (Mx) depending from the cheek plates 
(Ge). The sheath of the beak (Lb) is the labium. We 
have here, therefore, a most instructive lesson on the 
manner in which organs may be made over in form, by 
the processes of evolution, adapting them to new and 
often highly special uses. 

The abdomen of the cicada is thick, and strongly 
arched above. Its external appearance of plumpness 
suggests that it would furnish a juicy meal for a bird, 
and birds do destroy large numbers of the insects. Yet 
when the interior of a cicada is examined (Fig. 123), it is 
found that almost the entire abdomen is occupied by a 
great air chamber! The soft viscera are packed into 
narrow spaces about the air chamber, the stomach (Stom) 
being crowded forward into the rear part of the thorax. 

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The air chamber is a large, thin-walled sac of the tracheal 
respiratory system, and receives its air supply directly 
through the spiracles of the first abdominal segment. 
From the sac are given off" tracheal tubes to the muscles 
of the thorax and to the walls of the stomach. 

Many insects have tracheal air sacs of smaller size, 
and the purpose of the sacs in general appears to be that 
of holding reserve supplies of air for respiratory pur- 
poses. The great size of the air sac in the cicada's abdo- 
men, however, suggests that it has some special function, 
and it is natural to suppose that it acts as a resonating 
chamber in connection with the sound-producing drums. 
Yet the sac is as well developed in the female as in the 
male. Possibly, therefore, it serves too for giving buoy- 
ancy to the insects, for it can readily be seen that if the 
space occupied by the sac were filled with blood or other 
tissues, as it is in most other insects, the weight of the 
cicada would be greatly increased; or, on the other 
hand, if the body were contracted to such a size as to 
accommodate only its scanty viscera, it would lose 
buoyancy through lack of sufficient extent of surface — 
a paper bag crumpled up drops immediately when re- 
leased, but the same bag inflated almost floats in the air. 

The Sound-Producing Organs and the Song 

The cicadas produce their music by instruments quite 
different from those of any of the singing Orthoptera 
—the grasshoppers, katydids, and crickets, described 
in Chapter II. On the body of the male cicada, just 
back of the base of each hind wing, as we have already 
observed, in the position of the "ear" of the grasshopper 
(Fig. 63, Tm), there is an oval membrane like the head 
of a drum set into a solid frame of the body wall (Fig. 
120, Tm). Each drumhead, or tympanum, is a mem- 
brane closely ribbed with stiff vertical thickenings, the 
number ot ribs varying in different species of cicadas 
and perhaps accounting in part for the different qualities 

[ 207] 


of sound produced. In the periodical cicada, the drum- 
heads are exposed and are easily seen when the wings 
are lifted; in our other common cicadas each drum is 
concealed by a flap of the body wall. 

The sound made by an ordinary drum is produced by 
the vibration of the drumhead that is struck by the 
player, but the tone and volume of the sound are given 
by the air space within the drum and by the sympathetic 
vibration of the opposite head. The air within the 
drum, then, must be in communication with the air 
outside the drum, else it would impede the vibration of 
the drumheads. 

All these conditions imposed upon a drum are met bv 
the cicada. The abdomen of the insect, as we have seen, 
is largely occupied by a great air chamber (Fig. 123), 
and the air within the chamber communicates with the 
outside air through the spiracles of the first abdominal 
segment (ISp). In addition to the two drumheads whose 
activity produces the sound, there are two other thin, 
taut membranous areas set into oval frames in the lower 
side walls of the front part of the abdomen (not seen 
in the figures). These ventral drumheads have such 
smooth and glistening surfaces that they are often desig- 
nated the "mirrors." The wall of the air sac is applied 
closely to their inner surfaces, but both membranes are 
so thin that it is possible to see through them right into 
the hollow of the cicada's body. The ventral drum- 
heads are not exposed externally, however, for they are 
covered by two large, flat lobes projecting back beneath 
them from the under part of the thorax. 

The cicada does not beat its drums or play upon them 
with any external part of its body. When a male is 
"singing," the exposed drumheads are seen to be in very 
rapid vibration, as if endowed with the power of auto- 
matic movement. An inspection of the interior of the 
body of a dead specimen, however, shows that con- 
nected with the inner face of each drumhead is a thick 

I 208 1 


muscle which arises below from a special support on the 
ventral wall of the second abdominal segment (Figs. 
123, 124, TmMcl). It is by the contraction of these 
muscles that the drum membranes are set in motion. 







Fig. 1 24. The abdomen and sound-making organs of the male periodical 


A, the abdomen cut open from above, exposing the air chamber {AirSc), and 
showing the great tympanal muscles {TmMcl) inserted on the tympana (Tm). 
The arrows indicate the position of the first spiracles opening into the air chamber 

(see fig. 123, ISp) 

B, inner view of right half of first and second abdominal segments, showing the 

ribbed tympanum {Tm), and the muscles that vibrate it (TmMcl) 
AirSc) air chamber; DMcI, dorsal muscles; IS, IIS, HIS, sternal plates of first 
three abdominal segments; ISp, first abdominal spiracle; IT, IIT, HIT, tergal 
plates of first three abdominal segments; Nz, tergal plate of third thoracic seg- 
ment; T?n, tympanum; TmMcl, tympanal muscle; ?Vz, base of hind wing; VMcl, 
ventral muscles 

But a muscle pulls in only one direction; the drum muscles 
produce directly the inward stroke of the drumhead 
membranes; the return stroke results from the outward 
convexity and the elasticity of the heads themselves 
and the stiff ribs in their walls. 

When a cicada starts its music, it lifts the abdomen a 
little, thus opening the space between its ventral drum- 

[ 209] 


heads and the protecting flaps beneath, and the sound 
comes out in perceptibly increased volume. There can 
be little doubt that the air chamber of the body and the 
ventral membranes are important accessories in the 
sound-producing apparatus. Living cicadas are often 
found with half or more of the abdomen broken off, leav- 
ing the air sac open to the exterior. Such individuals 
may vibrate the drumheads, but the sound produced is 
weak and entirely lacks the quality of that made by the 
perfect insect. 

Wherever the periodical cicada appears in great num- 
bers, the daily choruses of the males leave an impression 
long remembered in the neighborhood; and, curiously, 
the sound appears to become increasingly louder in 
retrospect, until, after the lapse of years, each hearer is 
convinced it was a deafening clamor that almost deprived 
him of his senses. Fortunately the cicadas are day- 
time performers and are seldom heard at night. The 
song of the periodical species has no resemblance to the 
shrill, undulating screech of the annual cicadas so com- 
mon every summer in August and September. All the 
notes of the more common large form of the seventeen- 
year race are characterized by a burr sound, and at 
least four different utterances may be distinguished; the 
quality of three of the notes probably depends on the 
age of the individual insect, the fourth is an expression 
of fright or anger. 

The simplest notes to be heard are soft purring sounds, 
generally made by solitary insects sitting low in the 
bushes, probably individuals that have but recently 
emerged from the ground. The next is a longer and 
louder note, characterized by a rougher burr, lasting about 
five seconds, and always given a falling inflection at the 
close. This sound is the one popularly known as the 
"Pharaoh" song, because of a fancied resemblance to 
the name if the first syllable is sufficiently prolonged and 
the second allowed to drop off abruptly at the end. It 

[ 210] 


is repeated at intervals of from two to five seconds, and 
is given always as a solo by individuals sitting in the 
bushes or on lower branches of the trees. Males singing 
the Pharaoh song, therefore, are easily observed in the 
act of performing. With the beginning of each note, the 
singer lifts his abdomen to a rigid, horizontal position, 
thus opening the cavity beneath the lower drumheads 
and letting out the full volume of the sound. Toward the 
end of the note, the abdomen drops again to the usual 
somewhat sagging position, appearing thus to give the 
abrupt falling inflection at the close. 

The grand choruses, by which the periodical cicada is 
chiefly known and remembered, are given by the fully 
matured males of the swarm, always high in the trees 
where the singers may seldom be closely observed while 
performing. The individual notes are prolonged bur-r-r-r- 
like sounds, repeated all day and day after day, but all 
single voices are blended and lost in the continuous hum 
of the multitude. 

The fourth note of the larger form of the cicada is 
uttered by males when they appear to be surprised or 
frightened. On such occasions, as the insect darts 
away, he makes a loud, rough sound, and the same note 
is often uttered when a male is picked up or otherwise 

The notes of the small form of the seventeen-year race 
of the cicada have an entirely different character from 
those of his larger relative. The regular song of the little 
males much more resembles that of the annual summer 
cicadas, though it is not so long and is less continuous 
in tone. It opens with a few short chirps; then follows 
a series of strong, shrill sounds like zwing, zwing, zwing, 
and so on, closing again with a number of chirps. The 
whole song lasts about fifteen seconds. Several of these 
males kept in cages for observation sang this song re- 
peatedly and no other. It is common out of doors, but 
always heard in solo, never in chorus. When handled 



or otherwise disturbed, the small males utter a succession 
of sharp chirps very suggestive of the notes of some 
miniature wren angrily scolding at an intruder. Never 
does the small form of the cicada utter notes having the 
burr tone of those of the larger species, and the vocal 
differences of the two varieties are strikingly evident 
when several males of both kinds are caged together. 
When disturbed, each produces his own sound, one the 
burr, the other the chirp; and there is never any sugges- 
tion of similarity or of gradation between them. 

Egg Laving 

The cicadas lay their eggs in the twigs of trees and 
shrubs and frequently in the stalks of deciduous plants. 
They show no particular choice of species except that 
conifers are usually avoided. 

The eggs are not stuck into the wood at random, but 
are carefully placed in skillfully constructed nests which 
the female excavates in the twigs with the blades of her 
ovipositor (Plate 8). These nests are perhaps always 
on the under surfaces of the twigs, unless the latter are 
vertical, and usually there are rows of from half a dozen 
to twenty or more of them together. 

Egg laying begins in the early part of June, and by 
the tenth of June it is at its height. The female cicadas 
can easily be watched at work, taking flight only from 
actual interference. They usually select twigs of last 
year's growth, but often use older ones or green ones of 
the same season. In the majority of cases the female 
works outward on the twig; but if this is a rule, it is a 
very loosely observed one, for many work in the opposite 

Each nest is double; that is, it consists of two chambers 
having a common exit, but separated by a thin vertical 
partition of wood ( Plate 8, D, F). The eggs are placed 
on end in the chambers in two rows, with their head ends 



Egg punctures and the eggs of the periodical cicada 

A, B, C, twigs of dogwood, oak, and apple containing rows of cicada 
egg nests. D, cross-section of a twig through an egg nest, showing the 
two chambers, each containing a double row of eggs. E, vertical 
lengthwise section through two egg nests, showing the rows of slanting 
eggs and the frayed lip of the nest opening. F, horizontal section 
showing each chamber filled with a double row of eggs. G, several eaas 

(much enlarged) 


downward and slanted toward the door. Generally there 
are six or seven eggs in each row (E), making twenty-four 
to twenty-eight eggs in the whole nest, but frequently 
there are more than this. The wood fibers at the en- 
trance are much frayed by the action of the ovipositor 
and make a fan-shaped platform in front of the door 
(A, B, C). Here the young shed their hatching garments 
on emerging from the nest. The series of cuts in the bark 
eventually run together into a continuous slit, the edges 
of which shrink back so that the row of nests comes to have 
the appearance of being made in a long groove. This 
mutilation kills many twigs, especially those of oaks and 
hickories, the former soon showing the attacks of the 
insects by the dying leaves. The landscape of oak- 
covered regions thus becomes spotted all over with red- 
brown patches which often almost cover individual trees 
from top to bottom. Other trees are not so much in- 
jured directly, but the weakened twigs often break in the 
wind and then hang down and die. 

An ovipositing female (Plate 7) finishes each egg nest 
in about twenty-five minutes; that is, she digs it out and 
fills it with eggs in this length of time, for each chamber 
is filled as it is excavated. A female about to oviposit 
alights on a twig, moves around to the under surface, 
and selects a place that suits her. Then, elevating the 
abdomen, she turns her ovipositor forward out of its 
sheath and directs its tip perpendicularly against the bark. 
As the point enters it goes backward, and when in at full 
length the shaft slants at an angle of about forty-five 

In a number of cases females were frightened away at 
different stages of their work, and an examination of the 
unfinished nests showed that each chamber is filled with 
eggs as soon as it is excavated; that is, the insect com- 
pletes one chamber first and fills it with eggs, then digs 
out the other chamber which in turn receives its quota of 
eggs, and the whole job is done. The female now moves 



forward a few steps and begins work on another nest, 
which is completed in the same fashion. Some series 
consist of only three or four nests, while others contain 
as many as twenty and a few even more, but perhaps 
eight to twelve are the usual numbers. When the female 
has finished what she deems sufficient on one twig, she 
flies away and is said to make further layings elsewhere, 
till she has disposed oi her 400 to 600 eggs, but the writer 
made no observations covering this point. Probably 
the cicada feels it safer not to intrust all her eggs to one 
tree, on the principle of not putting all your money in the 
same bank. 

Death of the Adults 

The din of music in the trees continues with monot- 
onous regularity into the second week of June, by which 
time the mating season is over. Soon thereafter the per- 
formers lose their vitality; large numbers of them drop 
to the earth where many perish from an internal fungus 
disease that eats off the terminal rings of the body; 
others are mutilated and destroyed by birds, and the 
rest perhaps just die a natural death. Beneath the trees, 
where a great swarm has but recently given such abundant 
evidence of life, the ground is now strewn with the dead 
or dying. A large percentage of the living are in various 
stages of disfigurement — wings are torn off, abdomens are 
broken open or gone entirely, mere fragments crawl about, 
still alive if the head and thorax are intact. In the males 
often the great muscle columns of the drums are exposed 
and visibly quivering, and many of the insects, game to 
the end, even in their dilapidated condition still utter 
purring remnants of their song. 

From now on till the latter part of July, the only evi- 
dence of the late swarm of noisy visitors will be the scarred 
twigs on the trees and bushes that have received the eggs 
and the red-brown patches of dying leaves that every- 
where disfigure the oaks and hickories. 



Tke Broods 

The two races of the periodical cicada, the seventeen- 
year and the thirteen-year, together occupy most of the 
eastern part of the United States, except the northern 
part of New England, the southeastern corner of Georgia, 
and the peninsula of Florida. The western limits extend 
into the eastern part of Nebraska, Kansas, Oklahoma, 
and Texas. In general, the seventeen-year race is north- 
ern, and the thirteen-year race is southern, but, though 
the geographic line between the two races is remarkably 
distinct, there is considerable overlapping. 

While the two cicada races are distinguished from each 
other by the length of their life cycle, the members of each 
race do not all appear in the adult stage in any one year. 
Both the seventeen-year race and the thirteen-year race 
are broken up into groups of individuals that emerge in 
different years, and these groups are known as "broods." 
Each brood has its definite year of emergence, and in 
general a pretty well-defined territory. The territories of 
the different broods, however, overlap, or the range of a 
small brood may be included in that of a larger one. 
Hence, in any particular locality, there is not always an 
interval of thirteen or seventeen years between the ap- 
pearance of the insects; and it may happen that members 
of a thirteen-year brood and of a seventeen-year brood 
will emerge in the same year at the same place. 

The emergence years of the principal cicada broods 
have now been recorded for a long time, and the oldest 
record of a swarm is that of the appearance of the "locusts" 
in New England two hundred and ninety-five years ago. 
A full account of the broods of both races of the periodical 
cicada, their distribution, and the dates of their emergence, 
is given in Dr. C. L. Marlatt's Bulletin, already cited, and 
the following abstract is taken from this source: 

Wherever a well-defined cicada brood appears in a 
certain year, it is generally observed that a few individuals 

[2i 5 ] 


come out the year before or the year after. This fact has 
suggested the idea that the various broods established at 
the present time had their origin from individuals of a 
primary brood that, as we might say, got their dates 
mixed, and came out a year too soon or a year too late, 
the multiplying descendants of these individuals thus 
founding a new brood dated a year in advance or a year 
behind the emergence time of the parent stock. In this 
way, it is conceivable, the seventeen-year race might come 
to appear on each of seventeen consecutive years, and the 
thirteen-year race on each of thirteen consecutive years. 
Individuals emerging on the eighteenth or fourteenth year, 
according to the race, would be reckoned as a part of the 
first brood of its race. 

The facts known concerning the emergence of the 
cicadas seem to confirm the above theory, for members of 
the seventeen-year race appear somewhere every year 
within the limits of their range, and the emergence of 
members of the thirteen-year race has been recorded for at 
least eleven out of the possible thirteen years. All the 
individuals of a brood are not, of course, descendants of a 
single group of ancestors, nor do they necessarily occur 
together in a restricted area — they are simply individuals 
that coincide in the year of their emergence. However, at 
least thirteen of the broods of the seventeen-year race are 
well defined groups, for the most part with definitely circum- 
scribed territories, though overlapping in many cases. The 
broods of the thirteen-year race are not so well developed. 

The broods are conveniently designated by Roman 
numerals. According to the system of brood numbering 
proposed by Doctor Marlatt, and now generally adopted, 
the brood of the seventeen-year race that appeared last in 
1927 is Brood I. This is not a large brood, but it has 
representatives in Pennsylvania, Maryland, District of 
Columbia, Virginia, West Virginia, North Carolina, 
Kentucky, Indiana, Illinois, and eastern Kansas. Brood 
II, 1928, lives in the Middle Atlantic States, with a few 

I 216 I 


scattering colonies farther west. Brood III, 1929, is 
mostly confined to Iowa, Illinois, and Missouri. The 
largest of the broods is X, covering almost the entire range 
of the seventeen-year race. This brood made its last 
appearance in 19 19, and is due next, therefore, in 1936. 
The series of broods as numbered thus follows the suc- 
cessive years to Brood XVII, the last brood of the seven- 
teen-year race, which will return next in 1943. 

The small and uncertain broods of the seventeen-year 
race are VII, XII, XV, XVI, and XVII. The cicadas 
that emerge in the vears corresponding with these num- 
bers represent incipient broods, being probably the 
descendants of a few individuals that sometime became 
separated from the larger broods of the years preceding 
or following. One of the smallest of the seventeen-year 
broods is XI, but since its colonies occur in Massachu- 
setts, Connecticut, and Rhode Island, it is likely that it 
was more numerous in individuals in former times than 
at present. The brood with the oldest recorded history 
is XIV. This is a large brood extending over much of 
the range of the seventeen-year race, with colonies in 
eastern Massachusetts on Cape Cod and near Plymouth, 
the emergence of which was observed bv the early settlers 
probably in 1634. 

The broods of the thirteen-year race are numbered 
from XVIII to XXX, Brood XVIII being that which 
appeared last in 1919. But there are only two important 
broods of this southern race, XIX, which emerged in 
1920, and XXII, which emerged in 1924. In most of the 
other years the shorter-lived race is represented by only 
a few individuals that emerge here and there over its 
range; and none at all are known to appear during the 
years corresponding with the numbers XXV and XXVIII. 

The Hatching of the Eggs 

Five weeks have elapsed since the departure of the 
cicada swarms. It is nearly six weeks since egg laying 



was at its height, and the eggs are now due to hatch almost 
any time. When studying the cicadas of Brood X near 
Washington in 1919, the writer found the first evidence 
of hatching on the twenty-fourth of July. Perhaps the 
normal time of hatching had been delayed somewhat by 
heavy rains that fell almost continuously during the ten 
days previous, for many eggs examined during this time 
were found to be dead and turning brown, though the 
percentage of these was small. The twenty-fifth was hot 
and bright all day. The trees were inspected in the 
afternoon. Their twigs had been bare the day before. 
Now, at the entrance holes of the egg nests were little 
heaps of shriveled skins, thousands in all, and each so 
light that the merest breath of air sufficed to blow it off; 
so, if according to this evidence thousands of nymphs had 
hatched and gone, the evidence of as many more must 
have been carried away by the winds. An examination 
of many egg nests themselves showed that over half con- 
tained nothing but empty shells. Whole series were thus 
deserted, and usually all or nearly all, of the eggs in any 
one series of nests would be either hatched or unhatched. 
But often the eggs ot one or more nests would be un- 
hatched or mostly so in a series containing otherwise only 
empty shells. Delay appeared to go by nests rather than 
by individual eggs. 

As a very general rule the eggs nearest the door of an 
egg chamber are the ones that hatch first, the others 
following in succession, though not in absolute order. 
But unhatched eggs, if present, are always found at the 
bottom of the nest, with the usual exception of one or two 
farther forward. Only occasionally an empty shell occurs 
in the middle of an unhatched row. I f the actual hatching 
of the eggs is observed in an opened nest, several nymphs 
are usually seen coming out at the same time, and in 
nearly all cases they are in neighboring eggs, though not 
always contiguous ones. So this rule of hatching, like 
most rules, is general but not binding. 



The procedure of the female in placing the eggs leaves 
no doubt that the first-laid ones are those at the bottom of 
the cell, showing that the order of laying has no relation to 
the order of hatching, except that it is mostly the reverse. 
It seems hardly reasonable to suppose that the eggs nearest 
the door are affected by greater heat or by a fresher sup- 
ply of air, so it is suggested that the order of hatching 
may be due simply to the successive release of pressure 
along the tightly packed rows, giving the compressed 
embryos a chance to squirm and kick enough to split the 
inclosing shells. When hatching once commences it pro- 
ceeds very rapidly through the whole nest, showing that 
the eggs are all at the bursting point when the rupture of 
the first takes place. 

In each lateral compartment of an egg nest the eggs 
(Plate 8, E, F) stand in two rows with their lower or 
head ends slanted toward the door. (It must be re- 
membered that the punctures are made on the lower sides 
of the twigs, so that the eggs are inverted in their natural 
position in the nests.) On hatching, each egg splits ver- 
tically over the head and about one-third of the length 
along the back, but tor only a short distance on the 
ventral side. As soon as this rupture occurs, the head 
of the young cicada bulges out; and then, by a bending 
of the body back and forth, the creature slowly works its 
way out of the shell, which, when empty, remains behind 
in its original place. The nymphs nearest the door have 
an easy exit, but those from the depths of the cell find 
themselves still in a confined space between the project- 
ing ends of the empty shells ahead of them and the chamber 
wall, a passage almost as narrow as the egg itself, through 
which the delicate creatures must squirm to freedom. 

A newly-hatched or a newly-born aphid, as we have 
seen in Chapter VI, is done up in a tight-fitting garment 
with neither sleeves nor legs, but nature has been more 
considerate in the case of the young cicada. It, too, 
comes out of the egg clothed in a skin-tight jacket, but 



5 Discarded skin. 


7. Free nymph 

Fig. 125. The egg, the newly-hatched nymph shedding the embryonic 
skin, and the free nymph of the periodical cicada 



this garment is not a mere bag; it is provided with special 
pouches for the appendages or a part of them (Fig. 125, 2). 
The incased antennae and the labrum project backward 
as three small points lying against the breast. The 
front legs are free to the bases of the femora, though so 
tightly held in their narrow sleeves that their joints have 
no independent motion. The middle and hind legs are 
also incased in long, slim sheaths, but they always adhere 
close to the sides of the body. Thus the cicada nymph 
newly-hatched much resembles a tiny fish provided only 
with two sets of ventral fins, but when it gets into action 
its motions are comparable with the clumsy flopping of a 
seal stranded on the beach and trying to get back into 
the water (j). 

The infant cicada knows it is not destined to spend its 
life in the narrow cavern of its birth, or at least it has no 
desire to do so. With its head pointed toward the exit, 
it begins at once contortionistic bendings of the body, 
which slowly drive it forward. By throwing the head 
and thorax back, the antenna] tips and the front legs are 
made to project so that their points may take hold on 
any irregularity in the path. Then a contractile wave 
running forward through the abdomen brings up the rear 
parts of the body as the front parts are again bent back, 
and the "flippers" grasp a new point of support. As 
these motions are repeated over and over again, the tiny, 
awkward thing painfully but surely moves forward, per- 
haps helped in its progress bv the inclined tips of the 
flexible eggshells pressing against it, on the same prin- 
ciple that a head of barley automatically crawls up the 
inside of your sleeve. 

Once out of the door no time is lost in discarding the 
encumbering garment, but it is never shed in the nest 
under normal conditions. If, however, the nest is cut 
open and the hatching nymph finds itself in a free, open 
space, the embryonic sheath is cast off immediately, often 
while the posterior end of the insect's body is still in the 

f 221 1 


egg, so that the skin may be left sticking in the open end 
of the shell. If the young cicada did not have to gain its 
liberty through that narrow corridor, it might be born 
in a smooth bag as are its relations, the aphids. 

Watching at the door of an undisturbed nest during a 
hatching day, we soon may see a tiny pointed head come 
poking out of the narrow hole. The threshold is soon 
crossed, but no more; this traveling in a bag is not a 
pleasure trip. A few contortions are always necessary 
to rupture the skin, and sometimes several minutes are 
consumed in violent twistings and bendings before it 
splits. When it does break, a vertical rent is formed 
over the top ot the head, which latter bulges out until 
the cleft becomes a circle that enlarges as the entire head 
pushes through, followed rapidly by the body (Fig. i 25, /). 
The appendages come out ot their sheaths like fingers out 
of a glove, turning the pouches outside in. The antennae 
are free first; they pop out and hang stiffly downward. 
Then the front legs are released and hang stiff and rigid 
but quivering with a violent trembling. In a second or 
so this has passed, the joints double up and assume the 
characteristic attitude, while they violently claw the air. 
Then the other legs and the abdomen come out and the 
embryo is a free young cicada (7). All this usually 
happens in less than a minute, and the new creature is 
already off without so much as a backward glance at 
the clothes it has just removed or at the home of its in- 
cubation period. Sentiment has no place in the insect 

As the nymphs emerge from the nest, one after an- 
other, and shed their skins, the glistening white mem- 
branes accumulate in a loose pile before the entrance, 
where they remain until wafted off on the breeze. Each 
discarded sheath has a goblet form (Fig. 125, 5, 6), the 
upper stiff part remaining open like a bowl, the lower 
part shriveling to a twisted stalk. The antennal and 
labral pouches project from the skin as distinct append- 

[ 222 ] 


ages, but those of the legs are usually inverted during 
the shedding and disappear from the outside of the slough, 
though the holes where they were pulled in can be found 
before the membrane becomes too dry. 

The nymph (Figs. 125, 7; 126) usually runs about at 
first in the groove of the twig containing its egg nest and 
then goes out on the smooth bark. Here any current 
of air is likely to carry it off immediately, but many 
wander about for some time, usually going toward the 
tips of the twigs, some even getting clear out on the leaves. 
But only a few nymphs are ever to be found on twigs 
where piles of embryonic skins show that hundreds have 
recently hatched; so it is evident that the great majority 
either fall off or are blown away very shortly after emerg- 
ing. Many undoubtedly fall before the shedding of the 
egg membrane, for the inclosed creature has no possible 
way of holding on, and even the free nymph has but feeble 
clinging powers. Those observed on twigs kept indoors 
often fell helplessly from the smooth bark while appar- 
ently making real efforts to retain their grasp. Their 
weak claws could get no grip on the hard surface. In- 
stead, then, of deliberately launching themselves into 
space in response to some mysterious call from below, 
the young cicadas simply fall from their birthplace by 
mere inability to hold on. But the same end is gained — 
they reach the ground, which is all that matters. Nature 
is ever careless of the means, so long as the object is at- 
tained. Some acts of unreasoning creatures are assured 
by bestowing an instinct, others are forced by with- 
holding the means of acting otherwise. 

The cicada nymphs are at first attracted by the light. 
Those allowed to hatch on a table in a room will leave 
the twigs and head straight for the windows ten feet 
away. This instinct under natural conditions serves to 
entice the young insects toward the outer parts of the 
tree, where they have the best chance of a clear drop 
to earth; but even so, adverse breezes, irregularity of the 

[ 223 ] 


trees, underbrush, and weeds can not but make their 
downward journey one of many a bump and slide from 
leaf to leaf before the earth receives them. 

The creatures are too small to be followed with the eye 
as they drop, and so their actual course and their be- 
havior when the ground is reached are not recorded. But 
several hatched indoors were placed on loose earth packed 

Fig. i 26. The young cicada nymph ready to enter the ground (greatly enlarged) 

flat in a small dish. These at once proceeded to get be- 
low the surface. They did not dig in, but simply entered 
the first crevice that they met in running about. If the 
first happened to terminate abruptly, the nymph came 
out again and tried another. In a few minutes all had 
found satisfactory retreats and remained below. The 
eagerness with which the insects dived into any opening 
that presents itself indicates that the call to enter the 
earth is instinctive and imperative once their feet have 
touched the ground. Note, then, how within a few 
minutes their instincts shift to opposites: on hatching, 
their first effort is to extricate themselves from the narrow 
confines ot the egg nest, and it seems unlikely that enough 
light can penetrate the depths of this chamber to guide 
them to the exit; but once out and divested of their en- 
cumbering embryonic clothes, the insects are irresistibly 
drawn in the direction of the strongest light, even though 
this takes them upward — just the opposite of their 


destined course. When this instinct has served its purpose 
and has taken the creatures to the port of freest passage 
to the earth, all their love of light is lost or swallowed up 
in the call to enter some dark crevice narrower even than 
the one so recently left by such physical exertion. 

When the young cicadas have entered the earth we 
practically have to say good-bye to them until their 
return. Yet this recurring event is ever full of interest 
to us, for, much as the cicadas have been studied, it seems 
that there is still plenty to be learned from them each 
time they make their visit to our part of the world. 



The fascination of mythology and the charm of fairy 
tales lie in the power of the characters to change their 
form or to be changed by others. Zeus would court the 
lovely Semele, but knowing well she could not endure the 
radiance of a god, he takes the form of a mortal. Omit 
the metamorphosis, and what becomes of the myth? 
And who would remember the story of Cinderella if the 
fairy godmother were left out? The flirtation between 
the heroine and the prince, the triumph of beauty, the 
chagrin of the haughty sisters — these are but ingredients 
in the pot of common fiction. But the transformation 
of rats into prancing horses, of lizards into coachman 
and lackeys, of rags into fine raiment — this imparts the 
thrill that endures a lifetime! 

It is not surprising, then, that the insects, by reason 
of the never-ending marvel of their transformations, hold 
first place in every course of nature study in our modern 
schools, or that nature writers of all times have found a 
principal source of inspiration in the "wonders of insect 
life." Nor, finally, should it be made a matter of scorn 
if the insects have attached themselves to our emotions, 
knowing how ardently the natural human mind craves a 
sign of the supernatural. The butterfly, spirit of the 
lowly caterpillar, has thus been exalted as a symbol of 
human resurrection, and its image, carved on graveyard 
gates, still offers hope to those unfortunates interred 
behind the walls. 

Metamorphosis is a magic word, in spite of its formidable 

[ 226 ] 


appearance; but rendered into English it means simply 
"change of form." Not every change of form, however, is 
a metamorphosis. The change of a kitten into a cat, of 
a child into a grown-up, of a small fish into a large fish 
are not examples of metamorphosis, at least not of what 
is called metamorphosis. There must be something spec- 
tacular or unexpected about the change, as in the trans- 
formation of the tadpole into a frog, the change of the 
wormlike caterpillar into a moth, or of a maggot into a 

Fig. 127. Moths of the fall webworm 

fly. This arbitrary limiting of the use of a word that 
might, from its derivation, have a much more general 
meaning, is a common practice in science, and for this 
reason every scientific term must be defined. Meta- 
morphosis, then, as it is used in biology, signifies not 
merely a change of form, but a particular kind or degree 
of change; the kind of change, we might say, that would 
appear to lie outside the direct line of development from 
the egg to the adult. 

At once it becomes evident that, by reason of the very 
definition we have adopted, our subject is going to be- 
come complicated; for how are we to decide if an observed 
change during the growth of an animal is in line or out of 
line with direct development? There, indeed, lies a seri- 
ous difficulty, and we can only leave it to the biologist to 
decide in any particularly doubtful case. But there are 
plenty of cases concerning which there is no doubt. A 



caterpillar, for example, certainly is not a form headed 
toward a butterfly in its growth, and yet we know it is a 
young butterfly because it hatches out of the butterfly's 
egg. And, as the caterpillar grows from a small cater- 
pillar to a large caterpillar, it becomes no more like a 
butterfly than it was at first. It is only after it has 
reached maturity as a caterpillar that it undergoes a 
process of transformation by which it attains at last the 
form of the insect that produced it. 

The question now arises as to whether the butterfly is a 
form superadded to the caterpillar, or the caterpillar a 
form that has deviated from the developmental line of 
its ancestors. This question is easily answered: the but- 
terfly represents the true adult form of its species, for it 
has the essential structure of all other insects, and it alone 
matures the sexual organs and acquires the power of re- 
production. The caterpillar is an aberrant form that 
somehow has been interpolated between the egg and the 
adult of its kind . The real metamorphosis in the life of 
the butterfly, therefore, is not the change of the cater- 
pillar into the adult, but the change of the butterfly 
embryo in the egg into a caterpillar. Yet the term is 
usually applied to the reverse process by which the 
caterpillar is turned back into the normal form of its 

The caterpillar and the butterfly (Fig. 128) furnish the 
classical example of insect metamorphosis. Many other 
insects, however, undergo the same kind of transforma- 
tion. All the moths as well as the butterflies are cater- 
pillars when they are young: the famous giant moths 
(Plate 10), including the Cecropia, the Promethea, and the 
beautiful Luna (Fig. 129), as every nature student knows, 
come from huge fat caterpillars; the humble cutworms 
(Fig. 130), when their work of destruction is completed, 
change into those familiar brown or gray furry moths of 
moderate size (A) often found hidden away in the day- 
time and attracted to lights at night. In the spring, the 



Two species of large moths, natural size, showing the beautiful markings 

and colors with which even night-flying insects may be adorned. 

Upper figure, Heliconisa arpi Schaus, from Brazil; lower, Dirphia 

carminata Schaus, from Mexico. (From J. M. Aldrich) 


Fig. 128. The cellery caterpillar, and the butterfly into which it transforms 



May beetles, or "June bugs" appear (Fig. 131 A); they are 
the parents of the common white grubs (B) which every 
gardener will recognize. The common ladybird beetles 
(Fig. 132 A) are the adults of the ugly larvae (D) that feed 
so voraciously on aphids. In the comb of the beehive or 

Fig. 129. The Luna moth 

of the wasps' nest, there are many cells that contain small, 
legless, wormlike creatures; these are the young bees or 
wasps, but you would never know it from their structure, 
for they have scarcely anything in common with their 
parents (Fig. 133 A, B). The young mosquito (Fig. 174 
D) we all know, from seeing it often pictured and de- 
scribed and from observing that mosquitoes abound 
wherever these wigglers are allowed to live. The young 

[ 230) 






Two species of giant moths 

Upper figure, the Cecropia moth, female; lower, the Polyphemus moth, 

male. (From A. H. Clark) 


fly is a maggot (Fig. 182 D). The maggots of the house 
fly inhabit manure piles; those of the blow fly live in dead 
animals where they feed on the decaying flesh. 

We might go on and fill a whole chapter, or a whole book 
for that matter, with descriptions of the forms that insects 
go through in their metamorphoses, but since other writers 
have demonstrated that this can be done and without ex- 


Fig. 130. The life of a cutworm 
A, the parent moth. B, eggs laid by the moth on a blade of grass. C, a cut- 
worm at its characteristic night work, eating off a young garden plant at the 
root. D, other cutworms climbing the stalk of plants to feed on the leaves. 
E, the cutworm hidden within the earth during the day 

hausting the subject, we shall rather turn our attention 
here to what may be regarded as the deeper and more ab- 
struse phases of insect metamorphosis. Where the tacts 
themselves are highly interesting, the explanation of them 
must be still more so. Explanations, however, are always 
more difficult to present than the facts that are to be ex- 


plained, and if a writer often does not succeed so well with 
the reader in this undertaking, the reader should remember 
that his own difficulties of reading are perhaps no greater 
than the difficulties of the writer in writing. With a little 
extra effort on both sides, then, we may be able to arrive 
at a mutual understanding. 

In the first place, let us see in what particular manner 
the young and the adults of insects differ from each other. 
The adult, of course, is the fully matured form, and it 
alone has the organs of reproduction functionally devel- 
oped; but this is true of all animals. The caterpillar and 
the moth, the grub and the beetle, the maggot and the fly, 
however, differ widely in many other respects, and are so 
diverse in appearance and in general structure that their 
identities can be known only by observing their transfor- 
mations. On the other hand, the young grasshopper 
(Fig. 8), the young roach (Fig. 51), or the young aphis 
(Fig. 97) is so much like its parents that its family rela- 
tionships are apparent on sight. Still, in the case of all 
winged insects, there is one persistent difference between 
the young and the adult, and this is with respect to the 
development of the wings. The wings are always imper- 
fect or lacking in the young. The inability to fly puts a 
limitation on the activities of the immature insect and 
compels it to seek its living by more ordinary modes of 
progression. It may inhabit the land or the water; it may 
live on the surface; it may burrow into the earth or into 
the stems or wood of plants — in short, it may live in a 
thousand different places, wherever legs or squirming 
movements will take it, but it can not invade the air, 
except as it may be carried by the wind. 

As a first principle in the study of metamorphosis, then, 
we must recognize the fact that only the adult insect is 
capable of flight. 

Let us now turn back to the grasshopper (Chapter I); 
it furnishes a good example of an insect in which the adults 
differ but little from the young, except in the matter of 



the wings and the organs of reproduction. As might be 
expected, therefore, the young grasshoppers and the 
adults live in the same places and eat the same kinds of 
food in the same way. This likewise is true of the roaches, 
the katydids, the crickets, the aphids, and other related 


Fig. 131. A May beetle and its grub 

A, the adult beetle which feeds on the leaves of shrubs and trees. 

B, the larva, a white grub, which lives in the ground and feeds 

on roots 

insects. The adults here take no advantage over the 
young in matters of everyday life by reason of their 

In many other insects, however, the adults have 
adopted new ways of living and particularly of feeding, 
made possible and advantageous to them because of their 
power of flight. Then, in adaptation to their new habits, 
they have acquired a special form of the body, of the 
mouth parts, or of the alimentary canal. But all such 
modifications, if thrust upon the young, would only be an 
impediment to them, because the young are not capable of 
flight. Take the dragonflies as an example. The adult 
dragonfly (Fig. 58) feeds on small insects which it catches 
in the air, and it can do so because it has a powerful flying 
mechanism. The young dragonfly (Figs. 59, 134), how- 
ever, could not follow the feeding habits of its parents; if it 
had to inherit the parental form of body and mouth parts 


it would be greatly handicapped for living its own life, and 
this would be quite as detrimental to the adult, which 
must be developed from the young. Therefore, nature 
has devised a scheme for separating the young from the 
adult, by which the latter is allowed to take full advan- 
tage of its wings without imposing a hardship or a dis- 
ability on its flightless offspring. The device sets aside 
the ordinary workings of heredity and makes it possible 
for a structural modification to be developed in the adult 
and to be suppressed in the young until the time of change 
from the last immature stage to that of the adult. 

Thus we may state as a second principle of metamor- 
phosis that an adult insect may develop structural characters 
adaptive to habits that depend on the power of flight, which 
are suppressed in the young, where they would he detrimental 
by reason of the lack of wings. 

When parents, now, assert their independence, what 
can we expect of the offspring? Certainly only a similar 
declaration of rights. A young insect, once freed from 
any obligation to follow in the anatomical footsteps of its 
progenitors, so long as it finally reverts to the form of the 
latter, soon adopts habits of its own; and then acquires 
a form, physical characters, and instincts adapted to such 
habits. Thus, the young dragonfly (Fig. 134) has de- 
parted from the path of its ancestors; it has adopted a life 
in the water, where it feeds upon living creatures which it 
pursues by its perfection in the art of swimming and cap- 
tures by a special grasping organ developed from the 
under lip (B). Life in the water, too, entails an adaptation 
for aquatic respiration. All the special acquisitions in 
the structure of the young insect, however, must be dis- 
carded at the time of its change to the adult. 

A third principle, then, which follows somewhat as a 
corollary from the second, shows us that the young of 
insects may adopt habits advantageous to themselves, and 
take on adaptive structures that have no regard to the form of 
the adult and that are discarded at the final transformation. 



The degree of departure of the young from the parental 
form varies much in different insects. In the cicada, for 
example, the nymph is not essentially different in structure 
from the adult except in the matter of the wings, the 
organs of reproduction and egg laying, and the musical 

Fig. 132. The life history of a ladybeetle, Adalia bipunclata 

A, the adult beetle. B, group of eggs on under surface of a leaf. C, a young 

larval beetle covered with white wax. D, the full-grown larva. E, the pupa 

attached to a leaf by the discarded larval skin 

instrument. But the habitats of the two forms are widely 
separated, and it is unquestionable that, in the case of the 
cicada, it is the nymph that has made the innovation in 
adopting an underground life, for with most of the rela- 
tives of the cicada the young live practically the same life 
as the adults. 

Animals live for business, not for pleasure; and all their 
instincts and their useful structures are developed for 
practical purposes. Therefore, where the young and the 
adult of any species differ in form or structure, we may be 
sure that each is modified for some particular purpose of 
its own. The two principal functions of any animal are 
the obtaining of food for its own sustenance, and the 

[ 2 3S] 


production of offspring. The adult insect is necessarily 
the reproductive stage, but in most cases it must support 
itself as well; the immature insect has no other direct 
object in lite than that of feeding and ot preparing itself 
for its transformation into the adult. The feeding func- 
tion, however, as we have seen in Chapter IV, involves 

Fig. 133. Wasps, or yellow jackets 

A, an adult male of Vespula maculata. 

B, C, D, larva, pupa, and adult worker of 
Vespula maculifrons. The worker is a non- 
reproductive female and uses her oviposi- 
tor as a sting 



most of the activities and structures of the animal, in- 
cluding its adaptation to its environment, its modes of 
locomotion, its devices tor avoiding enemies, its means of 
obtaining food. Hence, in studying any young insect, we 
must understand that we are dealing almost exclusively 
with characters that are adaptive to the feeding function. 
When we observe the life ot any caterpillar we soon 
realize that its principal business is that ot eating. The 
caterpillar is one creature, at least, that may openly pro- 
claim it lives to eat. Whatever else it does, except acts 



connected with its transformation, is subservient to the 
function of procuring food. Most species feed on plants 
and live in the open (Fig. 131; A); but some tunnel into the 
leaves (B), into the fruit (D), or into the stem or wood 
(C). Other species feed on seeds, stored grain, and cereal 
preparations. The caterpillars of the clothes moths, 
however, feed on animal wool, and a few other caterpillars 
are carnivorous. 

The whole structure of the caterpillar (Fig. 136) be- 
tokens its gluttonous habits. Its short legs (L, AbL) keep 
it in close contact with the food material; its long, thick, 
wormlike body accommodates an ample food storage and 
gives space for a large stomach for digestive purposes; its 
hard-walled head supports a pair of strong jaws {Md), and 
since the caterpillar has small use for eves or antennae, 
these organs are but little developed. The muscle system 
of the caterpillar presents a wonderful exhibition of com- 
plexity in anatomical structure, and gives the soft body of 
the insect the power of turning and twisting in every con- 
ceivable manner. In contrast to the caterpillar, the moth 
or the butterfly feeds but little, and its food consists of 
liquids, mostly the nectar of flowers, which is rich in 
sugars and high in energy-giving properties but contains 
little or -none of the tissue-building proteins. 

When we examine the young of other insects that 
differ markedly from the parent form, we discover the 
same thing about them, namely, the general adaptation of 
their body form and of their habits to the function of eat- 
ing. Not all, however, differ as widely from the parent 
as does the caterpillar from the moth. The young of 
some beetles, for example (Fig. 137), more closely re- 
semble the adults except for the lack of wings. Most of 
the adult beetles, too, are voracious feeders, and are per- 
haps not outdone in food consumption by the young. But 
here another advantage of the double life is demon- 
strated, for usually the grub and the adult beetle have 
different modes of life and live in quite different kinds of 



places. Each individual of the species, therefore, occupies 
at different times two distinct environments during its 
life and derives advantages from each. It is true that 
with some beetles, the young and the adults live together. 


Fig. 134. The nymph of a dragonfly 
A, the entire insect, showing the long underlip, or labium (Li), 
closed against the under surface of the head. B, the head and 
first segment of the thorax of the nymph, with the labium ready 
for action, showing the strong grasping hooks with which the 
insect captures living prey 

Such cases, however, are only examples of the general rule 
that all things in nature show gradations; but this condi- 
tion, instead of upsetting our generalizations, furnishes 
the key to evolution, by which so many riddles may be 

The grub of the bee or the wasp (Fig. 133 B) gives an 
excellent example of the extreme specialization in form 
that the young of an insect may take on. The creature 
spends its whole life in a cell of the comb or the nest where 



it is provided with food by the parents. Some of the 
wasps store paralyzed insects in the cells of the nest for 
the young to feed on; the bees give their young a diet of 
honey and pollen, with an admixture of a secretion from a 
pair of glands in their own bodies. The grubs have noth- 
ing to do but to eat; they have no legs, eyes, or antennae; 
each is a mere body with a mouth and a stomach. The 
adult bees consume much honey, which, like its con- 
stituent, nectar, is an energy-forming food; but they also 
eat a considerable quantity of protein-containing pollen. 
Yet it is a great advantage to the bees in their social life 
to have their young in the form of helpless grubs that 
must stay in their cells until full-grown, when, by a quick 
transformation, they can take on the adult form and be- 
come at once responsible members of the community. Any 
parents distracted by the incorrigibilities of their offspring 
in the adolescent stage can appreciate this. 

The young mosquito (Fig. 174 D, E) lives in the water, 
where it obtains its food, which consists of minute par- 
ticles of organic matter. Some species feed at the surface, 
others under the surface or at the bottom of the water. 
The young mosquito is legless and its only means of pro- 
gression through the water is by a wiggling movement 
of the soft cylindrical body. It spends much of its time, 
however, just beneath the surface, from which it hangs 
suspended by a tube that projects from near the rear end 
of the body. The tip of the tube just barely emerges 
above the water surface, where a circlet of small flaps 
spread out flat from its margin serves to keep the creature 
afloat. But the tube is primarily a respiratory device, for 
the two principal trunks of the tracheal system open at its 
end and thus allow the insect to breathe while its body is 

The adult mosquito (Fig. 174 A), as everybody knows, is 
a winged insect, the females of which feed on the blood of 
animals and must go after their victims by use of their 
wings. It is clear, therefore, that it would be quite im- 



possible for a young mosquito, deprived of the power of 
flight, to live the life of its parents and to feed after the 
manner of its mother. Hence, the young mosquito has 
adopted its own way of living and of feeding, and this has 
allowed the adult mosquitoes to perfect their specialties 
without inflicting a hereditary handicap on their offspring. 
Thus again we see the great advantage which the 
species as a whole derives from the double life of its 

The fly will only give another example of the same 
thing. The specialized form of the young fly, the maggot 
(Fig. 171), which is adapted to the requirements of quite 
a different kind of life from that of the adult fly, relieves 
the latter from all responsibility to its offspring. As a 
consequence, the adult fly has been able to adapt its 
structure, during the course of evolution, to a way of 
living best suited to its own purposes, unhampered as it 
would be if its characters were to be inherited by the 
young, to whom they would become a great impediment, 
and probably a fatal handicap. 

A fourth principle of metamorphosis, then, we may say, 
is that the species as a whole has acquired an advantage by 
a double mode of existence, which allows it to take advantage 
of two environments during its lifetime, one suited to the 
functions of the young, the other to the functions of the 

We noted, in passing, that the young insect is free to 
live its own life and to develop structures suited to its own 
purposes under one proviso, which is that it must even- 
tually revert to the form of the adult of its species. At 
the period of transformation, the particular characters of 
the young must be discarded, and those of the adult must 
be developed. 

Insects such as the grasshoppers, the katydids, the 
roaches, the dragonflies, the aphids, and the cicadas ap- 
pear in the adult form when the young sheds its skin for 
the last time. The change that has produced the adult, 

[ 240 ] 


however, began at an earlier period, and the apparently 
new creature was partially or almost entirely formed 
within the old skin before the latter was finally shed. 

Fig. 135. Various habitats of plant-feeding caterpillars 

A, a caterpillar feeding in the open on a leaf. B, leaf miners in an apple leaf, 

the trumpet miner at a, the serpentine miner at b. C, the corn borer feeding 

within a corn stalk. D, the apple worm, or larva of the codling moth, feeding 

at the core of an apple 

After the molt, only a tew last alterations in structure and 
some final adjustments are made while the wings and legs 
ot the creature that had been confined in the closely fitting 
skin expand to their full length. The structural changes 
accomplished after the molt, however, vary with different 



species of insects, and with some they involve a consider- 
able degree of actual growth and change in the form of 
certain parts. The true transformation process, then, is 
really a period of rapid reconstructive growth preceding 
and following the molt, in which the shedding of the skin 
is a mere incident like the raising of the curtain for a new 
act in a play. During the intermission the actors have 
changed their costumes, the old scenery has been re- 
moved, and the new has been set in place. Thus it is 

Th Ab 


Fig. 136. Externa! structure of a caterpillar 

Ab, abdomen; AbL, abdominal legs; //, head; L\ y Lz, Z.3, the thoracic legs; Md, 

.jaws; Sp, breathing apertures; Tb, thoracic segments 

with the insect at the time of its transformation — the 
special accouterments of the young have been removed, 
and those ot the adult have been put on. 

The life of the insect, however, would not make a good 
theatrical production; it is too much of the nature of two 
plays given by the same set of actors. The young insect 
is dressed for a performance of its own in a stage setting 
appropriate to its act; the adult gives another play and is 
costumed accordingly. The actor is the same in each 
case only in the continuity of his individuality. His 
rehabilitation between the two acts will differ in degree 
according to the disparity between the parts he plays, 
that is, according to how far each impersonation is re- 
moved from his natural self. 

It is evident, therefore, that the transformation changes 
of an insect will differ in degree, or quantity, according to 

f 242] 


the sum of the departure of the young and the departure of 
the adult from what would have been the normal line of devel- 
opment if neither had become structurally adapted to a special 
kind of life. 

We may express this idea graphically by a diagram 
(Fig. 138), in which the line nm represents what might 
have been the straight course of evolution if neither the 
adult (/) nor the young (L) had departed along special 
lines of their own. But, when the adult and the young 
have diverged from some point (a) in their past history, 
the line LI, which is the sum of nm to L and of nm to /, 
represents the change which the young is bound to make 
in reverting to the adult form. The young must, there- 
tore, prepare itself tor this event in proportion as the 
distance LI is short or long. 

Where the structural disparity between the young and 
the adult is not great, or is mostly in the external form 
ot the body, the young insect changes directly into the 
adult, as we have seen in the case of the grasshopper 
(Fig. 9) and the cicada (Fig. 118). But with many in- 
sects, either because of the degree of difference that has 
arisen between the young and the adult, or for some 
other reason, the processes of transformation are not ac- 
complished so quickly and require a longer period for their 
completion. In such cases, the creature that issues at 
the last shedding of the skin by the young insect is in a 
very unfinished state, and must yet undergo a great 
amount ot reconstruction before it will attain the form 
and structure of the fully adult insect. This happens in 
all the groups of the more highly evolved insects, including 
the beetles; the moths and butterflies; the mosquitoes and 
flies; the wasps, bees, ants; and others. The newly 
transformed insect must remain in a helpless condition 
without the use of its legs and wings for a period of time 
varying in length with different species, until the adult 
organs, particularly the muscles, are completely formed. 

In the meantime, however, the soft cuticular layer of 



the skin of the newly emerged insect has hardened, 
thus preventing a further growth or change in the cellular 
layer of the body wall beneath it. Reorganization can 
proceed within the body, but the outer form is fixed and 

Fig. 137. Adult and larval form of beetles (Order Coleoptera) 
A, a ground beetle, Pterosticus. B, the same beetle with the right wings spread. 
C, the larva of Pterosticus. D, an adult beetle, Silpha surinamensis, with the 
left wings elevated. E, the larva of the same species, showing the similarity 
in structure to the adult (D) except for the lack of wings and the shortness of 

the legs 



must remain at the stage it had reached when the cuticula 
hardened. Only by a subsequent separation of this 
cuticula, allowing another period of growth in the cells of 
the body wall, can the form and the external organs of 
the adult be perfected. With another molt, therefore, 
the fully formed insect is at last set free, and it now re- 
quires only a short time for the expansion ot the legs and 
wings to their normal size and shape and for the hardening 
of the final cuticular layer which will preserve the contours 
of the adult. 

It thus comes about that the members of a large group 
of insects have acquired an extra stage in their life cycle, 
namely, a final reconstructive stage beginning some time 
before the last molt of the young and completed with a final 
added molt which liberates the fully formed adult. The 
insect in this stage is called a pupa. The entire pupal 
stage is divided by the last molting of the young into a 
propupal period, still occupying the loosened cuticula of 
the insect in its last adolescent stage, and a true pupal 
period, which is that between the shedding of this last 
skin of the young and the final molt which discloses the 
matured insect. 

All insects that undergo a metamorphosis may be 
divided, therefore, into two classes according as the trans- 
formation from the young into the adult is direct or is 
completed in an intervening pupal stage. Insects of the 
first class are said to have incomplete metamorphosis; those 
of the second class, complete metamorphosis. The ex- 
pressions are convenient, but misleading if taken literally, 
for, as we shall see, there are many degrees of "complete" 

The young of any insect that has a pupal stage in its 
life cycle is called a larva, and the young of an insect 
that does not have a pupal stage is termed a nymph, ac- 
cording to the modern custom of American entomologists. 
But the term "larva" was formerly applied to the im- 
mature stage of all' insects, a usage which should have 



been preserved; and many European entomologists use 
the word "nymph" for the stage we call a pupa. 

A larva is distinguished from a nymph by the lack of 
wing rudiments visible externally, and by the absence of 
the compound eyes. Many larvae are blind, but some 
of them have a group of simple eyes on each side of the 
head substituting for the compound eyes. Nymphs in 
general have the compound eyes of the adult insect, and, 
as seen in the young grasshopper 
m (Fig. 9), the young dragonfly (Fig. 59), 

and the young cicada (Fig. 114), the 
L nymphal wings are small pads that 
grow from the thoracic segments after 
the first or second molt. The larva, 
however, is not actually wingless any 
more than is the nymph; its wings are 
simply developed internally instead 
of externally. When the groups of 
cells that are destined to form the 
wings begin to multiply, the wing 
rudiments push inward instead of 
outward, and become small sacs in- 
vaginated into the cavity of the body, 
in which position they remain through 
all the active life of the larva. Then, 
at the time of the transformation, the 
wing sacs are everted, and appear on 
the outside of the pupa when the last 
larval skin is cast off. 

It is difficult to discover any neces- 
sary correlation between the exter- 
nally wingless condition of the larva 
and the existence of a pupal stage in 
the life of the insect; but the two for 
some reason go together. Perhaps it 
is only a coincidence. To have use- 
less organs removed from the surface 


Fig. 138. Diagram of 

If during the course of 
their evolution, the 
adult (/) and the larva 
(Z,)have independently 
diverged from a straight 
line of development 
(«w), the larva must 
finally attain the adult 
stage by a transforma- 
tion (metamorphosis), 
the degree of which is 
represented by the 
length of the line L to / 


is undoubtedly an advantage to a larva, especially to 
such species as live in narrow spaces, or that burrow into 
the ground or into the stems and twigs of plants; but 
it probably just happened that the pupal stage was first 
developed in an insect that had ingrowing wings. 

The typical larvae are the caterpillars, the grubs, and 
the maggots, young insects with little or no resemblance 
to their parents. The larvae of 
some of the beetles (Fig. 137) and 
of some members of the order 
Neuroptera, however, are much 
like the adults of their species, 
except for the lack of external 
wings and the compound eyes; 
and even among the typical 
larvae some species have more of 
the adult characters than others. 
The caterpillar (Fig. 136) or the 
grub of the May-beetle (Fig. 131 
B), for example, both being pro- 
vided with legs, have a much 
greater resemblance to an adult 
insect than has the wormlike leg- 
less grub of the wasp (Fig. 133 B) 
or the maggot of the fly (Fig. 
182 D). Hence, we see, the de- 
gree of transformation may vary 
much even among insects that 
have a so-called "complete" 

There are a few insects that have no metamorphosis at 
all. These are wingless insects belonging to the groups 
known as Collembola and Thysanura (Figs. 57, 139, 140) 
and are probably direct descendants from the primitive 
wingless ancestors of the winged insects. These insects 
during their growth shed the skin at intervals, but they 
do not undergo a change of form; they illustrate the 

I ^-47 ) 

Fig. 139. Springtails, mem- 
bers of the Order Collembola, 
insects perhaps directly de- 
scended from the unknown 
wingless ancestors of winged 


normal procedure of growth by direct development from 
the embryo to the adult. 

It must appear that the nymph, or young of an insect 
with incomplete metamorphosis, is merely an aberrant 
development of the normal form of the young as it 
occurs in an insect without metamorphosis. This is 
evident from the fact that the nymph has external wings, 
fully developed compound eyes, and in general the same 
details of structure in the legs and other parts of the body 
as has the adult. Most larvae, on the other hand, have 
few or none of the structural details 
of the adult that might be expected to 
occur in a normal postembryonic ado- 
lescent form; but they do have many 
characters that appear to belong to a 
primitive stage of evolution and that 
we might expect to find in an em- 
bryonic stage of development. The 
caterpillar, for example, has legs on 
the abdomen (Fig. 136, AbL), an 
embryonic feature possessed by none 
of the higher insects in the adult 
stage; it has only one claw on its 
thoracic legs, a character of crusta- 
ceans and myriapods, but not of adult 
winged insects or of nymphs. Like- 
wise, there are certain features of the 
internal structure of the caterpillar 
that are more primitive than in any 
adult insect or nymph; and the same 
evidence of primitive or embryonic 
characters might be cited of other 
larvae. On the other hand, the structural details of some 
larvae are very much like those of the adults, and such 
larvae differ from the adults of their species principally 
in the lack of the compound eyes and of external wings. 
Now, if all the insects with complete metamorphosis 


Fic. I40. A bristle- 
tail, Thermobia, a mem- 
ber of the order Thy- 
sanura, another primi- 
tive group of wingless 
insects, (Twice natu- 
ral size) 


have been derived from a common ancestor, as seems 
almost certain, then the original larvae must have been 
all alike, and they must have had approximately the 
structure of those larvae of the present time that depart 
least from the structure of the adult. Therefore it is 
evident that many larvae of the present time have some- 
how acquired certain embryonic characters. We may 
suppose, therefore, either that such larvae have had a 
retrogressive evolution into the embryonic stage by 
hatching at successively earlier ages, or that certain 
embryonic characters representing ancestral characters 
but ordinarily quickly passed over in the embryonic 
development, have been retained and carried on into the 
larval stage. The latter view seems the more probable 
when we consider that no larva has a purely embryonic 
structure, and that those larvae which have embryonic 
features in their anatomy present an incongruous mixture 
of embryonic and adult characters. 

We may, therefore, finally conclude that the larva of 
insects with complete metamorphosis represents the nymphal 
stage of insects with incomplete metamorphosis; and that 
the structure of the larva has resulted from a suppression of 
the peculiarly adult characters, from an invagination of the 
wings, a loss of the compound eyes, the retention of certain 
embryonic characters, and a special development of the body 
form and the organs suited to the particular mode of life of 
the larva. By allowing for variations in all these elements 
that contribute to the larval make-up, except the two 
constants — the invagination of the wings and the loss of 
the compound eyes — we may account for all the variety 
in form and structure that the larva presents. 

While, in general, the larva remains the same in struc- 
ture from the time it is hatched until it transforms to the 
pupa, there are nearly always minor changes observable 
that are characteristic of its individual stages. In 
Chapter I we encountered the case of the little blister 
beetle that goes through several very different forms dur- 



ing its development (Figs. 12, 13), and other examples of 
a metamorphosis during the larval life might be given 
from the other groups of insects. A larval metamorphosis 
of this kind is known as hypermetamorphosis , and it shows 
that the larva may be structurally diversified during its 
growth to adapt it to several different environments or 
ways of obtaining its food. 

The reader was given fair warning that the subject of 
insect metamorphosis would become difficult to follow, 
and even now, with its realization, the writer can not 
assure him that the above analysis is by any means com- 
plete or final. Much more might be said for which there 
is no space here, and it is not likely that all entomologists 
will accept all that has been said without a discussion, 
and possibly some dissension. However, we have not 
yet reached the end, for we have so far been dealing only 
with the phase of metamorphosis that has produced the 
nymph or the larva, and have only briefly touched upon 
the reverse process which reconverts the creature into the 

The pupa unquestionably has the aspect of an imma- 
ture adult. It has lost all the characteristic features of 
the larva, and its organs are those of the adult in the 
making. It has external wing pads, legs, antennae, com- 
pound eyes. Its mouth parts are usually in a stage of 
development intermediate between those of the larva and 
those of the adult. Most of the pupal organs are useless, 
since they are neither those of the larva nor entirely those 
of the adult, and are not adapted to any special use the 
pupa might make of them, except in a very few cases. 
The pupa is, therefore, a helpless creature, unable to 
eat, or to make any movement except by motions of the 
body. It is usually said to be a "resting" stage, but its 
rest is an enforced immobility, and some species attest 
their impatience by an almost continuous squirming, 
twisting, or wriggling of the movable parts of the body. 

It is evident that it must be an advantage to the pupa 



to have some kind of protection, either from the weather, 
or from predacious creatures that might destroy it. While 
most pupae are protected in one way or another, there are 
some that remain in exposed situations with no kind of 
shelter or concealment. The mosquito pupa is one of 
these, for it lives in the water along with the larva and 
floats just beneath the surface (Fig. 174 F), breathing 
by a pair of trumpetlike tubes that project above the 
surface from the anterior part of the body. The mos- 
quito pupa is a very active creature, and can propel itself 
through the water, usually downward, with almost as 
much agility as can the larva, and by this means probably 
avoids its enemies. The pupa of the common lady-beetle 
gives another example of an unprotected pupa (Fig. 
132 E). The larvae of these insects transform on the 
leaves where they have been feeding, and the pupae re- 
main here attached to the leaf, unable to move except by 
bending the body up and down. The pupae of some of 
the butterflies also hang naked from the stems or leaves 
of plants. 

The pupae of many different kinds of insects are to be 
found in the ground, beneath stones, under the bark of 
trees, or in tunnels of the leaves, twigs, or wood of plants 
where the larvae have spent their lives. Some of these, 
especially beetle pupae, are naked, soft-bodied creatures, 
depending on their concealment for protection. The 
pupae of moths and butterflies, however, are character- 
istically smooth, hard-shelled objects with the outlines 
of the legs and wings apparently sculptured on the sur- 
face (Plate 14 F). Pupae of this kind are called chrysa- 
lides (singular, chrysalis). Their dense covering is formed 
of a gluelike substance, exuded from the skin, that dries 
and forms a hard coating over the entire outer surface, 
binding the antennae, legs, and wings close to the body. 
In addition, the pupae of many moths are inclosed in a 
silk cocoon spun by the caterpillar. The caterpillars, 
as we shall learn in the next chapter, are provided with 



a pair of silk-producing glands which open through a hol- 
low spine on the lower lip beneath the mouth (Fig. 155). 
The silk is used by the caterpillars during the feeding 
part of their lives in various ways, but it serves particu- 
larly for the construction of the cocoon. The most 
highly perfected instinct of the caterpillar is that which 
impels it to build the cocoon, often an intricately woven 
structure, just before the time of its transformation to 
the pupa. The caterpillar spins the cocoon around itself, 
then sheds its skin, which is thrust into the rear end of 
the cocoon as a crumpled wad. Plate 1 1 shows the cater- 
pillar of a small moth that infests apple trees constructing 
its cocoon, finally inclosing itself within the latter, and 
there transforming to the pupa. 

The larvae of the wasps and bees likewise inclose them- 
selves within cocoons formed inside the cells of the comb 
in which thev have been reared. The cocoon is made of 
threads, but the material is soft, and the freshly spun 
strands run together into a sheet that dries as a parch- 
mentlike lining of the cell. The larvae of many of the 
wasplike parasitic insects that feed within the bodies of 
other living insects leave their hosts when ready for trans- 
formation, and spin cocoons either near the deserted host 
or on its bod v. 

The maggots, or larvae, of the flies have adopted an- 
other method of acquiring protection during the pupal 
stage. Instead of shedding the loosened cuticula previ- 
ous to the transformation, the maggot transforms within 
the skin, and the latter then shrinks and hardens until it 
becomes a tough oval capsule inclosing the larva (Fig. 
182 E). The capsule is called a puparium. It appears, 
however, that the larva within the puparium undergoes an- 
other molt before it actually becomes a pupa, for, when the 
pupa is formed, it is found to be surrounded by a delicate 
membranous sheath inside the hard wall of the puparium, 
and when the adult fly issues it leaves this sheath and a 
thin pupal skin behind in the puparial shell. 



The ribbed-cocoon maker {Bucculatrix pomifoliella), a small caterpillar 

that inhabits apple leaves 
At A the caterpillar is spinning a mat of silk on the surface of a twig. 
B shows the silk thread issuing from the spinneret (a) on the under 
lip of the caterpillar. At C the caterpillar is erecting a line of silk 
palisades around the site of the cocoon. D and E show the cocoon in 
the course of construction, built on the silk mat. F is a diagram of 
the cocoon on under surface of the support, containing the pupa (g) 
and the shed skin of the caterpillar {h). G shows the interior of the 
cocoon, its double walls (c, d), and partitions (/) at the front end. 
H is the finished cocoon surrounded by the palisades 


The pupa has so many of the characters of the mature 
insect that we might say it is self-evident that it is a part 
of the adult stage, except that to say anything is "self- 
evident" is almost an unpardonable remark in scientific 
writing. However, it is clear to the eve that the pupa, 
in casting off the skin of the larva, has entirely discarded 
the larval form, except in certain insects that have a 
larval form in the adult stage. The pupa may retain a 
few unimportant larval characters, hut all its principal 
organs are those of an adult insect in a halfway sta^e of 
development. In studying the cicada, it. was observed 
that the adult issues from the skin of the nymph in a very 
immature condition. A careful dissection of a specimen 
at this time would show that the creature is still imperfect 
in many ways besides those which appear externally. By 
very rapid growth during the course of an hour, however, 
the adult form and organs are perfected. We have also 
noted that with insects of incomplete metamorphosis the 
adult is mostly formed within the nymphal skin some 
time before the latter is cast off. The same thing is true 
of a pupa. For several days before the caterpillar is 
ready to molt the last time, it remains almost motionless 
and its body contracts to perhaps less than half of the 
original length. The caterpillar is now said to be in a 
"prepupal" stage, but examination of a specimen will 
reveal that it has already transformed, tor inside its skin 
is a soft pupa in a preliminary stage of development 
(Fig. 141 B). 

This first stage of the pupa of a moth or butterfly (Fig. 
141 B) is entirely comparable with the immature adult 
of the cicada formed inside the skin of the last stage of 
the nymph (Fig. 141 A). The entire pupal period, 
therefore, corresponds with the formative stage of the 
cicada, which begins within the nymphal skin and is com- 
pleted about an hour after the emergence. The only 
external difference between the two cases is that the pupa 
sheds its skin, making a final added molt before it becomes 



a perfect insect, while the immature adult cicada goes 
over into the fully mature form quickly and without a 

We may conclude, therefore, that the pupa of insects 
with complete metamorphosis corresponds with the immature 
stage of the adult in insects with incomplete metamorphosis. 
This idea concerning the nature of the insect pupa has 

been well expressed and 
more fully substantiated 
by E. Poyarkoff, and it 
appears to have more in 
its favor than the older 
view that the pupa cor- 
responds with the last 
nymphal stage in insects 
with incomplete meta- 
morphosis. According 
to Poyarkoff's theory, 
the pupa has no phylo- 
genetic significance, that 
is, it does not represent 
any free-living stage in 
the evolution or ances- 
tral history of insects; 
it is simply a prolonged 
resting period following 
the shedding of the last 
larval skin, which termi- 
nates with an added 
molt when the adult is 
fully formed. 

It frequently happens 
that a pupa has some 
of the adult characters 
better developed than 
has the adult itself. The 
pupae of insects that 


Fig. 141. Showing the resemblance of 
the pupa of an insect with complete 
metamorphosis to the immature adult 
form of an insect with incomplete meta- 
A, immature adult cicada, taken from the 
last nymphal skin. B, immature pupa 
of a moth, taken from the last larval 
skin. C, the mature pupa of a wasp 

[ 254 1 


The peach-borer moth (Aegeria exitiosa) 

Upper figure, the adult male moth (about twice natural size); 

lower figure, the cocoon made by the caterpillar from bits of 

wood, with the empty shell of the pupa projecting from the 

opened end 


have rudimentary or shortened wings in the adult stage 
often have wings larger than those of the adult, indicat- 
ing that the wings have been reduced in the adult since 
the time when the pupa was first established. Here, 
therefore, we see a case of metamorphosis between the 
pupa and the adult. Adult moths and butterflies have no 
mandibles or have mere rudiments of them (Fig. 163), 
but the jaws are often quite visible in the pupae (Fig. 
159 H, Md), and the pupa of one moth has long, toothed 
mandibles which it uses to liberate itself from the cocoon 
before transforming to the adult. 

The structural changes that accompany the transfor- 
mation of the larva into an adult insect are by no means 
confined to the outside of the body. Much internal re- 
organization goes on which involves changes in the tissues 
themselves. The larva may have built up a highly effi- 
cient alimentary canal well adapted for handling its own 
particular kind of food, but perhaps the adult has adopted 
an entirely different diet. The alimentary canal, there- 
fore, must be completely remodeled during the pupal 
stage. The nervous system and the tracheal system are 
often different in the larval and the adult stages, but the 
change in these organs is usually in the nature of a greater 
elaboration for the purposes of the adult, though the 
larva may have developed special features that are dis- 

It is in the muscles usually that the most radical re- 
constructive processes of the transformation from larva to 
adult take place. The muscles of adult insects are at- 
tached to the outer cuticular layer of the body wall, which 
in hard-bodied insects constitutes the "skeleton," and the 
mechanical differences between the larva and the adult 
lie in the relation between the muscles and the cuticula. 
With the change in the external parts between the two 
active stages of the insect, therefore, the larval muscles 
are likely to become entirely unsuited to the purposes of 
the adult. The special larval muscles, then, must be 

I *55 ] 


cleared away, and a new muscle system must be built up 
suitable to the adult mechanism. Most of the other 
organs are transformed by a gradual replacement of cells in 
their tissues, with the result that each organ itself remains 
intact during the whole period of its alteration — the 
insect is never without a complete alimentary canal, its 
body wall always maintains a continuous surface. This 
condition, however, is not entirely true of the muscles, 
for with some insects undergoing a high degree of meta- 
morphosis in external structure, the muscular system may 
suffer a complete disorganization, the fibers of the larval 
system being in a state ot dissolution while those of the 
adult are in the process of development. 

'Hie muscles of adult insects, as we have just said, are 

attached to the outer 
layer of the body wall 
( Fig. 1 42). This layer 
is composed partly of 
a substance called 
chitin formed by the 
cellular layer ot the 
body wall beneath it, 
and constitutes the 
cuticular skin that is 
shed when the insect 
molts. The newly- 
formed cuticula is soft 
and takes the con- 
tour ot the cellular 
layer producing it. 

The muscles of the 
larva that go over 
into the adult stage 
and the new muscles ot the adult must become fastened 
to the new cuticula, and this is possible only when the 
cuticula is in the soft formative stage. It has been 
pointed out by PoyarkofF that, for this reason, whenever 

[ 256 ] 

Fig. 14a. Diagram of the attachment of a 
muscle to the body wall of an adult insect by 

means of the terminal fibrillae (Tfbl) 
BM, basement membrane; Enct^ endocuticula; 
Epct, epicuticula; Epd y epidermis; Exct, 
exocuticula; Met, muscle; Tfbl y terminal 
fibrillae of the muscle anchored in the cuticula 


new muscles are formed in an insect a new cuticula must 
also be produced in order that the muscle fibers may 
become attached to the skeleton. New muscles com- 
pleted at the time of a molt may be anchored into the new 
cuticula formed at this time; but if the completion of the 
muscle tissue is delayed, the new fibers can become func- 
tional only by attaching themselves at the following molt. 
Conversely, if the new muscles are not perfected at the 
time of the last normal molt, the insect must have an 
extra molt later in order to give the muscles a functional 
connection with the body wall. 

Thus Poyarkoff would explain the origin of the pupal 
stage in the life cycle of the insect. His theory has much 
to commend it, for, as Poyarkoff shows in an analysis of 
the various processes accompanying metamorphosis, none 
of the changes in any of the organs other than the muscles 
would seem to necessitate the production of a new cutic- 
ula and thus involve an added molt. If insects with 
incomplete metamorphosis add new muscles for the 
adult stage, such muscles must be ready-formed at the 
time of the last nymphal molt; but it is probable that 
there are few such cases in this class of insects. 

Adopting Poyarkoff's theory, then, as the most plausi- 
ble explanation of why a pupal stage has become separated 
by a molt from the fully-matured adult stage, we may 
say that the reason for the pupa is probably to be found in 
the delayed growth of the adult muscles and in the conse- 
quent need of a new cuticula for their attachment. 

With a pupal stage once established, however, the pupa 
has undergone an evolution of its own, as has the larva 
and the adult, though to a smaller degree than either 
of these two active stages. The pupa is characteristically 
different in each of the orders of insects, and many of its 
features are clearly adaptations to its own mode of life. 

It is one thing to know the facts and to see the mean- 
ing of metamorphosis; it is quite another to understand 
how it has come about that an animal undergoes a meta- 



morphic transformation, and yet another to discover how 
the change is accomplished in the individual. Meta- 
morphosis can be only a special modification of general 
developmental growth, and growth toward maturity by 
the individual goes over the same field that the species 
traversed in its evolution. Yet, the individual in its 
development may depart widely from the path of its 
ancestors. It may make many a detour to the right or 
the left; it may speed up at one place and loiter along at 
another; and, since the individual is rather an army of 
cells than a single thing, certain groups of its cells may 
forge ahead or go off on a bypath, while others lag behind 
or stop for a rest. Only one condition is mandatory, and 
this is that the whole army shall finally arrive at the same 
point at the same time. In each species, the deviations 
from the ancestral path, traveled for many generations, 
have become themselves fixed and definite trails followed 
by all individuals of the species. The development of 
the individual, therefore, may thus come to be very 
different from the evolutionary history of its species; and 
the life history of an insect with complete metamorphosis 
is but an extreme example of the complex course that 
may result when a species leaves the path of direct de- 
velopment to wander in the fields along the way. 

The larva and the adult insect have become in many 
cases so divergent in structure, as a result of their separate 
departures from the ancestral path, that the embryo has 
become almost a double creature, comprising one set of 
cells that develop directly into the organs of the embryo 
and another set held in reserve to build up the adult 
organs at the end of the larval life. The characters of 
the adult are, of course, impressed upon the germ cells 
and must be carried over to the next generation through 
the embryo, but they can not be developed at the same 
time that the larval organs are functional. Conse- 
quently, the cells, that are to form the special tissues 
of the adult remain through the larval period as small 



groups or islands of cells in the larval tissues. These 
dormant cell groups are known as imaginal discs, or his- 
toblasts. {Imaginal is from imago, an image, referring 
to the adult; histoblast means a tissue bud.) 

When analyzed closely, the apparent "double" struc- 
ture of the embryo will be found to be only the result 
of an exaggeration of the usual processes of growth, ac- 
companied by an acceleration in certain tissues and a 
retardation in others. In general, wherever an adult 
organ is represented by an organ in the larva, even though 
the latter is greatly reduced, the cells that are to give this 
organ its adult form do not begin to develop until the 
larval growth is completed. But if an organ is lacking 
in the larval stage, the regenerative cells may start to 
develop at an earlier period — even in the embryo in a 
few cases. Hence, the remodeling of a larval organ in the 
pupal stage is only a completion of that organ s normal de- 
velopment, and the production of a "new" organ is only 
the deferred development of one that has been suppressed 
during the larval period. 

The special organs or forms ot organs that the larva 
has built up for its own purposes necessarily become 
useless when the larval life has been completed. Such 
organs, therefore, must be destroyed if they can not be 
directly made over into corresponding adult organs. 
Their tissues consequently undergo a process of dissolu- 
tion, called histolysis. It can not be explained at the pres- 
ent time what causes histolysis, or why it begins at a 
certain time and in particular tissues, but histolysis is 
only one of the physiological processes that depend 
probably on the action of enzymes. In some insects a 
part of the degenerating tissues of the larva is devoured 
during the pupal stage by ameboid cells of the blood, 
known as phagocytes. It was once supposed that the 
phagocytes are the active agents of the destruction of the 
larval tissues, but this now seems improbable, since histol- 
ysis takes place whether phagocytes are present or absent. 

[ 2 59 1 


While the larval tissues are undergoing dissolution, 
the adult tissues are being built up from those groups of 
dormant cells, the histoblasts, that have retained their 
vitality. Whatever it is that produces histolysis in the 
defunct larval tissues, it has no effect on the regenerative 
tissues, which now begin a period of active development, 
or histogenesis (i.e., tissue building), which results in the 
completion of the adult organs. In most of the organs 
the two processes, histolysis and histogenesis, are com- 
plemental to each other, the new tissues spreading as the 
old are dissolved, so that there is never a lack of con- 
tinuity in the parts undergoing reconstruction. It is only 
in the muscles, as we have already observed, that the 
old tissues are destroyed before the new ones are formed. 

Because of the high physiological activity [metabolism) 
going on within the pupa, the blood of the insect at this 
stage becomes filled with a great quantity of matter re- 
sulting from the dissolution of the larval tissues. During 
the pupal period, the insect takes no food nor does it 
discharge any waste materials — the substance of the 
growing tissues is derived from the debris of those degen- 
erating. But the transformation is not all direct. The 
insect is provided with an organ for converting some of 
the products of histolysis into proteid compounds that 
can be utilized by the tissues in histogenesis. This organ 
is the fat-body (see Chapter IV and Figure 158). During 
the larval life the cells of the fat body store up large 
quantities of fat, and in some insects glycogen, both of 
which energy-forming substances are discharged into the 
blood at the beginning of the pupal period. And now 
the fat cells become also active agents in the conversion 
of histolytic products into proteid bodies, probably by 
enzymes given off from their nuclei. These proteid 
bodies are finally also discharged into the blood, where 
they are absorbed as nutriment by the tissues of the 
newly-formed organs. At the close of the pupal period, 
the fat-body itself is often almost entirely consumed or 



The red-humped caterpillar (Schizura concinnd) 

A, the moth in position of repose (natural size). B, moth with wings 
spread. C, under surface of apple leaf, showing eggs at a, and young 
caterpillars feeding at b. D, a caterpillar in next to last stage of growth. 
E, full-grown caterpillars (one-half larger than natural size). F, two 
cocoons on ground among grass and dead leaves, one cut open showing 
caterpillar within before transforming to pupa 


is reduced to a few scattered cells, which build up the fat- 
body of the adult. 

The internal adult organs undergo a continuous develop- 
ment throughout the pupal period and are practically 
complete when the latter terminates with the molt to the 
adult. But the external parts, after quickly attaining a 
halfway stage of development at the beginning of the 
pupal metamorphosis are checked in their growth by the 
hardening of the cuticular covering of the body wall, and 
in their half-formed shape they must remain to the end 
of the pupal period. It is only by a subsequent growth 
of the cellular layer of the body wall beneath the loosened 
cuticula of the pupa that the external adult parts are 
finally perfected in structure; and it is only when the 
pupal cuticula is then cast off and the organs cramped 
within it are given freedom to expand that the adult 
insect at last appears in its fully mature form. 



The Life of a Caterpillar 

It is one of those bleak days of early spring that so often 
follow a period of warmth and sunshine, when living things 
seem led to believe the fine weather has come to stay. 

Out in the woods a band of little caterpillars is clinging 
to the surface of something that appears to be an oval 
swelling near the end of a twig on a wild cherry tree 
(Fig. I43). The tiny creatures, scarce a tenth of an inch 
in length, sit motionless, benumbed by the cold, many 
with bodies bent into half circles as if too nearly frozen 
to straighten out. Probably, however, they are all un- 
conscious and suffering nothing. Yet, if they were ca- 
pable of it, thev would be wondering what fate brought 
them into such a forbidding world. 

But fate in this case was disguised most likely in the 
warmth of yesterday, which induced the caterpillars to 
leave the eggs in which they had safely passed the winter. 
The empty eggshells are inside the spindle-shaped thing 
that looks so like a swelling of the twig, for in fact this is 
merely a protective covering over a mass of eggs glued 
fast to the bark. The surface of the covering is perfor- 
ated by many little holes from which the caterpillars 
emerged, and is swathed in a network of fine silk threads 
which the caterpillars spun over it to give themselves a 
surer footing and one they might cling to unconsciously 
in the event of adverse weather, such as that which makes 
them helpless now. When nature designs any creature 



The tent caterpillar (Malacosoma americana) 

A, an egg mass on an apple twig (about natural size). B, young 
caterpillar feeding on an opening leaf bud. C, branches of an apple 
tree with a tent in a fork, from which trails of silk lead outward to 
the twigs where the caterpillars are feeding on the leaves. D, a full- 
grown caterpillar (three-fourths natural size). E, cocoon. F, pupa, 
taken from a cocoon. G, male moth. H, female moth laying eggs 


to live under trying circumstances she grants it some 
safeguard against destruction. 

The web-spinning habit is one which, as we shall see, 
these caterpillars will develop to a much greater extent 
later in their lives, for our little acquaintances are young 
tent caterpillars. They are found most often among 
woodland trees, on the chokecherry and the wild black 
cherry. But they commonly infest apple trees in the 
orchards, and for this reason their species has been named 
the apple-tree tent caterpillar, to distinguish it from 
related forms. that do not com- 
monly inhabit cultivated fruit 
trees. The scientific name is 
Malacosoma americana. 

The egg masses of the tent 
caterpillar moths are not hard to 
find at this season. They are 
generally placed near the tips of 
the twigs, which they appear to 
surround, and being of the same 
brownish color as the bark, they 
look like swollen parts of the 
twigs themselves (Plate 14A, 
Fig. 144 A). Most of them are 
five-eighths to seven-eighths of 
an inch in length and almost half 
of this in width, but they vary in 
thickness with the diameter of 
the twig. A closer inspection shows that the mass really 
clasps the twig, or incloses it like a thick jacket lapped 
clear around. In form the masses are usually sym- 
metrical, tapering at each end, but some are of irregular 
shapes, and those that have been placed at a forking or 
against a bud have one end enlarged. 

The greater part of an egg mass consists of the cover- 
ing material, which is a brittle, filmy substance like dry 
mucilage. Some of it is often broken away, and some- 

[ 263 ] 

Fic. 143. Young tent cater- 
pillars on the egg mass from 
which they have just hatched. 
(i,!-4 times natural size) 


times the tops of the eggs are entirely bare. The eggs 
are placed in a single layer next the bark (Fig. 144 B), 
and there are usually 300 or 400 of them. They look like 
little, pale-gray porcelain jars packed closely together 
and glued to the twig by their rounded and somewhat 
compressed lower ends. The tops are flat or a little 
convex. Each egg is the twenty-fourth of an inch in 
height, about two-thirds of this in width, and has a 
capacity of one caterpillar. The covering is usually half 
again as deep as the height of the eggs, but varies in thick- 
ness in different specimens. The outer surface is smooth 
and polished, but the interior is full of irregular, many- 
sided air spaces, separated from one another by thin 
partitions (B). 

Wherever the covering of an egg mass has been broken 
away, the bases ot the partition walls leave brown lines 
that look like cords strapped and tied into an irregular 
net over the eggs (B), as if for double security against 
insurrection on the part of the inmates. But neither 
shells nor fastenings will offer effective resistance to the 
little caterpillars when they are taken with the urge for 
freedom. Each is provided with efficient cutting in- 
struments in the form of sharp-toothed jaws that will 
enable it to open a round hole through the roof of its cell 
(Fig. 1 44 C). The superstructure is then easily pene- 
trated, and the emerging caterpillar finds itself on the 
surlace of its former prison, along with several hundred 
brothers and sisters when all are out. 

All this time the members of that unfortunate brood 
we noted first have been clinging benumbed and motion- 
less to the silk network on the covering of their deserted 
eggs. The cold continues, the clouds are threatening, 
and during the afternoon the hapless creatures are 
drenched by hard and chilling rains. Through the night 
following they are tossed in a northwest gale, while the 
temperature drops below freezing. The next day the 
wind continues, and frost comes again at night. For three 



days the caterpillars endure the hostility of the elements, 
without food, without shelter. But already the buds on 
the cherry tree are sending out long green points, and 
when the temperature moderates on the fourth day and 

Fie. 144. Eggs and newly-hatched larvae of the 

tent caterpillar 
A, egg masses on twigs, about natural size. B, 
eggs exposed beneath the covering. C, several 
eggs (more enlarged) three with holes in the tops 
from which the young caterpillars have emerged. 
D, newly-hatched caterpillars (enlarged about 
nine times) 

the sun shines again for a brief 
period, the revived outcasts are 
able to find a few fresh tips on 
which to nibble. In another day 
the young leaves are unfolding, of- 
fering an abundance of tender for- 
age, and the season of adversity 
for these infant caterpillars is over. 
This family of tent caterpillars was 
hatched near Washington on the 
25th of March. 

The newly-hatched caterpillars 
(Fig. 144 D) are about one-tenth 
of an inch in length. The body is 
widest through the first segment 




and tapers somewhat toward the other end. The general 
color is blackish, but there is a pale gray collar on the 
first segment back of the head and a grayish line along 
the sides of the body. Most of the segments have pale 
rear margins above, which are often bright yellow or 
orange on the fourth to the seventh segments. There is 
usually a darker line along the middle of the back. The 
body is covered with long gray hairs, those on the sides 
spreading outward, those on the back curving forward. 
After a few days of feeding the caterpillars increase to 
nearly twice their length at hatching. 

When the weather continues fair after the time of 
hatching, the caterpillars begin their lives with happier 
days, and their early history is different from that of 
those unfortunates described above. Three other broods, 
which were found hatching on March 22, before the period 
of bad weather had begun, were brought indoors and 
reared under more favorable circumstances. These 
caterpillars spent but little time on the egg masses and 
wasted only a few strands of silk upon them. They were 
soon off on exploring expeditions, small processions going 
outward on the twigs leading from the eggs or their 
vicinity, while some individuals dropped at the ends of 
threads to see what might be below. Most, however, at 
first went upward, as if they knew the opening leaf buds 
should lie in that direction. If this course, though, hap- 
pened to lead them up a barren spur, a squirming, furry 
mob would collect on the summit, apparently bewildered 
by the trick their instinct had played upon them. On 
the other hand, many followed those that first dropped 
down on threads, these in turn adding other strands till 
soon a silken stairway was constructed on which indi- 
viduals or masses of little woolly bodies dangled and 
twisted, as if either enjoying the sport or too fearful to 
go farther. 

For several days the young caterpillars led this happy, 
irresponsible life, exploring twigs, feeding wherever an 

f 266 1 


open leaf bud was encountered, dangling in loose webs, 
but spinning threads everywhere. Yet, in each brood, 
the individuals kept within reach of one another, and the 
trails of silk leading back to the main branch always 
insured the possibility of a family reunion whenever this 
should be desired. 

One morning, the 27th, one family had gathered in its 
scattered members and these had already spun a little 
tentlike web in the 
crotch between the 
main stem of the sup- 
porting twig and two 
small branches (Fig. 
145). Some members 
were crawling on the 
surface of the tent, 
others were resting 
within, still others were 
traveling back and 
forth on the silk trails' 
leading outward on the 
branches, and the rest 
were massed about 
the buds devouring the 
young leaves. The es- 
tablishment of the tent 
marks the beginning of 
a change in the cater- 
pillars' lives; it entails 
responsibilities that de- 
mand a fixed course of 
daily living. In the lives of the tent caterpillars this 
point is what the beginning of school days is to us — the 
end of irresponsible freedom, and the beginning of sub- 
jection to conventional routine. 

Every tent caterpillar family that survives infancy 
eventually reaches the point where it begins the con- 


Fig. 145. First tent made by young tent 
caterpillars. (About half natural size) 


struction of a tent, but the early days are not always spent 
alike, even under similar circumstances, nor is the tent 
always begun in the same manner. 

In the State of Connecticut, where the season for both 
plants and insects is much later than in the latitude of 
Washington, three broods of tent caterpillars were ob- 
served hatching on April 8 of the same year. These 
caterpillars also met with dull and chilly weather that 
kept them huddled on their egg coverings for several 
days. After four days the temperature moderated suffi- 
ciently to allow the caterpillars to move about a little on 
the twigs, but none was seen feeding till the 14th — six 

days after the hatching. 
Yet they had increased 
in size to about one- 
eighth of an inch in 

Wherever these cater- 
pillars camped in their 
wanderings over the small 
apple trees they inhabit- 
ed, they spun a carpet 
of silk to rest upon, and 
there the whole family 
collected in such a 
crowded mass that it 
looked like a round, furry 
mat (Fig. 146). The car- 
pets afforded the cater- 
pillars a much safer bed 
than the bare, wet bark 
of the tree, for if the 
sleepers should become 
stupefied by cold the claws of their feet would mechanically 
hold them fast to the silk during the period of their help- 
lessness. The test came on the 1 6th and the night fol- 
lowing, when the campers were soaked by hard, cold rains 

[268 1 

Fig. 146. Young tent caterpillars matted 

on a flat sheet of web spun in the crotch 

between two branches. (About natural 



till they became so inert they seemed reduced to lifeless 
masses of soggy wool. On the afternoon of the 17th the 
temperature moderated, the sun came out a few times, 
the wetness evaporated from the trees, and most of the 
caterpillars revived sufficiently to move about a little and 
dry their fur. Though a few had been washed off the 
carpets by the violence of the storm and had perished 
on the ground, and in one camp about twenty dead were 
left behind on the web, the majority had survived. 

For several days after this, during better weather, the 
caterpillars of these families continued their free exist- 
ence, feeding at large on the opening buds, but returning 
during resting periods to the webs, or constructing new 
ones at more convenient places. Often each family split 
into several bands, each with its own retreat, yet all re- 
mained in communication by means of the silk trails the 
members left wherever they went. 

The camping sites were either against the surface of a 
branch or in the hollow of a crotch. Though the carpet- 
like webs stretched over these places were spun appar- 
ently only to give secure footing, those at the crotches 
often roofed over a space well protected beneath, and fre- 
quently many of the caterpillars crawled into these spaces 
to avail themselves of their shelter. Yet for twelve days 
none of the broods constructed webs designed for cover- 
ings. Then, on the morning of the 20th, one family was 
found to have spun several sheets of silk above the carpet 
on which its members had rested for a week, and all were 
now inside their first tent. These caterpillars were near- 
ing the end of their first stage, and two days later the 
first molted skins were found in the tent, fourteen days 
after the date of hatching. 

In Stage II the caterpillars have a new color pattern 
and one which begins to suggest that characteristic of the 
species in its more mature stages (Fig. 148). On the upper 
part of the sides the dark color is broken into a series of 
quadrate spots each spot partially split lengthwise by a 



light streak, and the whole series on each side is bordered 
above and below by distinct pale lines, the upper line 
often yellowish. Below the lower line there is a dark 
band, and below this another pale line just above the 
bases of the legs. The back of the first body segment 
has a brown transverse shield, and the last three segments 
are continuously brown, without spots or lines. 

From now on the tents increase rapidly in size by suc- 
cessive additions of web spun over the tops and sides, 
each new sheet covering a flat space between itself and the 
last. The old roofs thus become successively the floors 
of the new stories. The latter, of course, lap over on the 
sides, and many continue clear around and beneath the 
original structure; but since the tent was started in a 
crotch, the principal growth is upward with a continual 
expansion at the top. During the building period a 
symmetrical tent is really a beautiful object (Plate 14 C). 
Half hidden among the leaves, its silvery whiteness pleas- 
ingly contrasts with the green of the foliage; its smooth 
silk walls glisten where the sun falls upon them and reflect 
warm grays and purples from their shadows. 

The caterpillars have adopted now a community form 
of living; all feed together, all rest and digest at the same 
time, all work at the same time, and their days are divided 
into definite periods for each of their several duties. 
There is, however, no visible system of government or 
regulation, but with caterpillars acts are probably func- 
tions; that is, the urge probably comes from some physio- 
logical process going on within them, which may be in- 
fluenced somewhat by the weather. 

The activities of the day begin with breakfast. Early 
in the morning the family assembles on the tent roof, and 
about six-thirty, proceeds outward in one or several 
orderly columns on the branches. The leaves on the 
terminal twigs furnish the material for the meal. After 
two hours or more of feeding, appetites are appeased, and 



the caterpillars go back to the surface of the tent, usually 
by eight-thirty or nine o'clock. Here they do a little spin- 
ning on its walls, but no strenuous work is attempted at 

Fig. 147. Mature tent caterpillars feeding at night 

this time, and generally within half an hour the entire 
family is reassembled inside the tent. Most frequently 
the crowd collects first in the shady side of the outermost 
story, but as the morning advances the caterpillars seek 



the cooler inner chambers, where they remain hidden 
from view. 

In the early part of the afternoon a light lunch is taken. 
The usual hour is one o'clock, but there is no set time. 
Occasionally the participants appear shortly after eleven, 
sometimes at noon, and again not until two or three 
o'clock, and rarely as late as four. As they assemble 
on the roof of the tent they spin and weave again until 
all are ready to proceed to the feeding grounds. This 
meal lasts about an hour. When the caterpillars return 
to the tent they do a little more spinning before they 
retire for the afternoon siesta. Luncheon is not always 
fully attended and is more popular with caterpillars in 
the vounger stages, being dispensed with entirely, as we 
shall see, in the last stage. 

Dinner, in the evening, is the principal meal of the 
day, and again there is much variation in the time of 
service. Daily observations made on five Connecticut 
colonies from the 8th to the 26th of May gave six-thirty 
p.m. as the earliest record for the start of the evening 
feeding, and nine o'clock as the latest; but the dinner 
hour is preceded by a great activity of the prospective 
diners assembled on the outsides of the tents. Though 
the energy of the tent caterpillars is never excessive, it 
appears to reach its highest expression at this time. The 
tent roots are covered with restless throngs, most of the 
individuals busily occupied with the weaving of new web, 
working apparently in desperate haste as if a certain task 
had been set for them to finish before they should be 
allowed to eat. Possibly, though, the stimulus comes 
merely from a congestion of the silk reservoirs in their 
bodies, and the spinning of the thread affords relief. 

The tent caterpillar does not weave its web in regular 
loops of thread laid on by a methodical swinging of the 
head from side to side, which is the method of most 
caterpillars. It bends the entire body to one side, at- 



taches the thread as far back as it can reach, then runs 
forward a few paces and repeats the movement, sometimes 
on the same side, sometimes on the other. The direction 
in which the thread is carried, however, is a haphazard 
one, depending on the obstruction the spinner meets from 
others working in the same manner. Among the crowd of 
weavers there are always a few individuals that are not 
working, though they are just as active as the others. 
These are 

running = " = = = 1 

back and 
forth over 
the surface 
of the tent, 
like boarders 
awaiting the 
sound ot the 
dinner bell. 
they are in- 
dividuals that have finished their 
work by exhausting their supply 
of silk. 

At last the signal for dinner 
is sounded. It is heard by the 
caterpillars, though it is not 
audible to an outsider. A 
few respond at first and start 
off on one of the branches 
leading from the tent. Others 
follow, and presently a column 
is marching outward, usually 
keeping to the well-marked 
paths of silk till the dis- 
tant branches are reached. 
Here the line breaks up into 

Fig. I48. Mature tent cater- 
pillars. (Natural size) 



several sections which spread out over the foliage. The 
tent is soon deserted. For one, two, or three hours 
the repast continues, the diners often returning home 
late at night. Observations indicate that this is the 
regular habit of the tent caterpillar in its earlier stages, 
and perhaps up to the sixth or last stage of its life. In 
at least nine instances the writer noted entire colonies 
back in the tent for the night at hours ranging from 
nine to eleven p.m.; but sometimes a part of the crowd 
was still feeding when last observed. 

In describing the life of a community of insects it is 
seldom possible to make general statements that will 
apply to all the individuals. The best that a writer can 
do is to say what he sees most of the insects do, for, as in 
other communities, there are always those eccentric mem- 
bers who will not conform with the customs of the major- 
ity. Occasionally a solitary tent caterpillar may be seen 
feeding between regular mealtimes. Often one works 
alone on the tent, spinning and weaving long after its 
companions have quit and gone below lor the midday 
rest. Such a one appears to be afflicted with an over- 
developed sense of responsibility. Then, too, there is 
nearly always one among the group in the tent who can 
not get to sleep. He flops this way and that, striking his 
companions on either side and keeping them awake also. 
These are annoyed, but they do not retaliate; they seem 
to realize that their restless comrade has but a common 
caterpillar affliction and must be endured. 

Many of these little traits make the caterpillars seem 
almost human. But, of course, this is just a popular 
form of expression; in fact, it expresses an idea too popular 
— we take an over amount of satisfaction in referring to 
our faults as particularly human characteristics. What 
we really should say is not how much tent caterpillars 
are like us in their shortcomings, but how much we are 
still like tent caterpillars. We both revert more or less 
in our instincts to times before we lived in communities, 



to times when our ancestors lived as individuals irre- 
sponsible one to another. 

The tent caterpillars ordinarily shed their skins six 
times during their lives. At each molt the skin splits 
along the middle of the back on the first three body seg- 
ments and around the back of the head. It is then 
pushed off over the rear end of the body, usually in one 
piece, though most other caterpillars cast off the head 
covering separate from the skin of the body in all molts 
but the last. The moltings take place in the tent, except 
the molt of the caterpillar to the pupa, and each molt 
renders the caterpillars inactive for the greater part of 
two days. When most of them shed their skins at the 
same time there results an abrupt cessation of activity in 
the colony. By the time the caterpillars reach maturity 
the discarded skins in a tent outnumber the caterpillars 
five to one. 

The first stage ot the caterpillars, as already described 
(Fig. 144 D), suggests nothing of the color pattern of the 
later stages, but in Stage II the spots and stripes of the 
mature caterpillars begin to be formed. In succeeding 
stages the characters become more and more like those of 
the sixth or last stage (Plate 14 D, Fig. 148), when the 
colors are most intensified and their pattern best defined. 
Particularly striking now are the velvety black head with 
the gray collar behind; the black shield of the first seg- 
ment split with a medium zone of brown; the white stripe 
down the middle of the back; the large black lateral 
blotches, each inclosing a spot of silvery bluish white; the 
distinctly bluish color between and below the blotches; 
and the hump on the eleventh segment, where the median 
white line is almost obliterated by the crowding of the 
black from the sides. Yet the creatures wearing all this 
lavishness ot decoration make no ostentatious show, for the 
colors are all nicely subdued beneath the long reddish- 
brown hairs that clothe the body. In the last stage, the 
average full-grown caterpillar is about two inches long, 



but some reach a length of two and a half inches when 
fully stretched out. 

In Connecticut, the tent caterpillars begin to go into 
their sixth and last stage about the middle of May. They 
now change their habits in many ways, disregarding the 
conventionalities and refusing the responsibilities that 
bound them in their earlier stages. They do little if any 
spinning on the tent, not even keeping it in decent repair. 
They stay out all night to feed (Fig. 147), unless adverse 
weather interferes, thus merging dinner into breakfast in 
one long nocturnal repast. This is attested by observa- 
tions made through most of several nights, when the 
caterpillars of four colonies which went out at the usual 
time in the evenings were found feeding till at least four 
o'clock the following mornings, but were always back in 
the tents at seven-thirty a.m. When the caterpillars begin 
these all-night banquets, they dispense with the mid- 
day lunch, their crops being so crammed with food by 
morning that the entire day is required for its digestion. 
Some writers have described the tent caterpillars as 
nocturnal feeders, and some have said they feed three 
times a day. Both statements, it appears, are correct, 
but the observers have not noted that the two habits 
pertain to different periods of the caterpillars' history. 

At any time during the caterpillars' lives adverse 
weather conditions may upset their daily routine. For two 
weeks during May, days and nights had been fair and 
generally warm, but on the 17th the temperature did not 
get above 65 F., and in the afternoon threatening clouds 
covered the sky. In the evening light rains fell, but the 
caterpillars of the five colonies under observation came out 
as usual for dinner and were still feeding when last ob- 
served at nine p.m. Rains continued through the night, 
however, and the temperature stood almost stationary 
between 50 and 55 . 

The next morning three of the small trees containing the 
colonies were festooned with water-soaked caterpillars, all 



hanging motionless from leaves, petioles, and twigs, be- 
numbed with exposure and incapable of action — more 
miserable-looking insects could not be imagined. No in- 
stinct of protection, apparently, had prevailed over their 
appetites; till at last, overcome by wet and cold, they 
were saved only by some impulse that led them to grasp 
the support so firmly with the abdominal feet that they 
hung there mechanically when senses and power of move- 
ment were gone. Some clung by the hindmost pair of feet 
only, others grasped the support with all the abdominal 
feet. One colony and most of another were safely housed 
in their tents. These had evidently retreated before 
helplessness overtook them. 

By eight o ; clock in the morning many of the suspended 
caterpillars were sufficiently revived to resume activity. 
Some fed a little, others crawled feebly toward the tents. 
By 9:45 most were on their way home, and at 10:4 5 all 
were under shelter. 

Gentle rains fell during most of the day, but the tem- 
perature gradually rose to a maximum of 65 . Only a few 
caterpillars from the youngest colony came out to feed at 
noon. In the evening there was a hard, drenching rain, 
after which several caterpillars from two of the tents ap- 
peared for dinner. The next morning, the 19th, the tem- 
perature dropped to 49°, light rains continued, and not a 
caterpillar from any colony ventured out for breakfast. It 
looked as if they had learned their lesson; but it is more 
probable they were simply too cold and stiff to leave the 
tents. In the afternoon the sky cleared, the temperature 
rose, and the colonies resumed their normal life. 

The tent caterpillars' mode of feeding is to devour the 
leaves clear down to the midribs (Figs. 148, 149), and in 
this fashion they denude whole branches of the trees they 
inhabit. Since the caterpillars have big appetites, it some- 
times happens that a large colony in a small tree or several 
colonies in the same tree may strip the tree bare before 
they reach maturity. The writer never saw a colony 



reduced to this extremity by its own feeding, but produced 
similar conditions for one in a small apple tree by removing 
all the leaves. This was on May 19, and the caterpillars 
were mostly in their fifth stage. At seven o'clock in the 

evening the cater- 
pillars in this col- 
ony came out as 
usual, and, after 
doing the cus- 
tomary spinning 
on the tent, 
started off to get 
their dinner, sus- 
pecting nothing 
till they came to 
the cut-off ends 
of the branches. 
Then they were 
clearly bewildered 
— they returned 
and tried the 
course over again ; 
they tried another 
branch, all the 
other branches; 
but all ended 
alike in bare 
stumps. Yet there 
were the accus- 
tomed trails, and 
their instincts 
clearly said that 
silk paths led to 
food. So all night 
the caterpillars hunted for the missing leaves; they went 
over and over the same courses, but none ventured below 
the upper part of the trunk. By 3:45 in the morning 


Fig. 149. 

Twigs of choke cherry and of apple de- 
nuded by tent caterpillars 


many had given up and had gone back to the tent, but the 
rest continued the hopeless search. At seven-thirty a few 
bold explorers had discovered some remnants of water 
sprouts at the base of the tree and fed there till ten o'clock. 
At eleven all were back in the tent. 

At two o'clock in the afternoon the crowd was out again 
and a mass meeting was being held at the base of the tree. 
But nobody seemed to have any idea of what to do, and no 
leader rose to the occasion. A few cautious scouts were 
making investigations over the ground to the extent of a 
foot or a little more from the base of the trunk, but, though 
there were small apple trees on three sides five feet away, 
only one small caterpillar ventured off toward one of 
these. He, however, missed the mark by twelve inches 
and continued onward; but probably chance eventually 
rewarded him. At three p.m. the meeting broke up, 
and the members went home. They were not seen again 
that evening or the next morning. 

During this day, the 21st, and the next, an occasional 
caterpillar came out of the tent but soon returned, and it 
was not till the evening of the 22nd that a large number 
appeared. These once more explored the naked branches 
and traveled up and down the new paths on the trunk, but 
none was observed to leave the tree. On the 23rd and 
24th no caterpillars were seen. On the 25th the tent was 
opened and only two small individuals were found within 
it. Each of these was weak and flabby, its alimentary 
canal completely empty. But what had become of the 
rest? Probably they had wandered off unobserved one 
by one. Certainly there had been no organized migra- 
tion. Solitary caterpillars were subsequently found on a 
dozen or more small apple trees in the immediate vicinity. 
It is likely that most of these had molted and had gone 
into the last stage, since their time was ripe, but this was 
not determined. 

After the caterpillars go over into their last stage, the 
tents are neglected and rapidly fall into a state of dilapida- 

[ 279] 


tion. Birds often poke holes in them with their bills and 
rip off sheets of silk which they carry away for nest-build- 
ing purposes. The caterpillars do not even repair these 
damages. The rooms of the tent become filled with ac- 
cumulations ot frass, molted skins, and the shriveled 
bodies of dead caterpillars. The walls are discolored by 
rains which beat into the openings and soak through the 
refuse. Thus, what were shapely objects of glistening silk 
are transmuted into formless masses of dirty rags. 

But the caterpillars, now in their finest dress, are ob- 
livious of their sordid surroundings and sleep all day 
amidst these disgusting and apparently insanitary condi- 
tions. However, the life in the tents will soon be over; 
so it appears the caterpillars simply think, "What's the 
use?" But of course caterpillars do not think; they arrive 
at results by instinct, in this case by the lack of an instinct, 
tor they have no impulse to keep the tents clean or in 

repair when doing so 
would be energy wasted. 
Nature demands a prac- 
tical reason for most 

The tent lite continues 
about a week after the 
last molt, and then the 
family begins to break 
up, the members leaving 
singly or in bands, but al- 
ways as individuals with- 
out further concern for 
one another. Judging 
from their previous me- 
thodical habits, one would suppose that the caterpillars 
starting off on their journeys would simply go down the 
trunks of the trees and walk away. But no; once in their 
life they must have a dramatic moment. A caterpillar 
comes rushing out of a tent as if suddenly awakened from 


Fig. 150. A tent caterpillar in the last 
stage of its growth, leaving the tree con- 
taining its nest by jumping from the end 
of a twig to the ground 


some terrible dream or as if pursued by a demon, hurries 
outward along a branch, goes to the end of a spur or the 
tip of a leaf, and without slackening continues into space 
till the end of the support tickles his stomach, when sud- 
denly he gives a flip into the air, turns a somersault, and 
lands on the ground (Fig. 150). 

The first performance of this sort was observed on 
May 1 <; in the Connecticut colonies. On the afternoon 
of the 19th, twenty or more caterpillars from two neigh- 
boring colonies were seen leaving the trees in the same 
fashion within half an hour. Most of the members of one 
of these colonies had their last molt on May 12 and 13. 
During the next few davs other caterpillars were ob- 
served jumping from four trees containing colonies under 
observation. All of these went off individually at various 
times, but most of them early in the afternoon. Many 
caterpillars simply drop off when they reach the end of 
the branch, without the acrobatic touch, but only three 
were seen to go down the trunk of a tree in commonplace 

The population of the tents gradually decreases during 
several days following the time when the first caterpillar 
departs. One of the two tents from which the general 
exodus was noted on May 19 was opened on the 21st and 
was found to contain only one remaining caterpillar. On 
the evening of the 22nd a solitary individual was out feed- 
ing from the other tent. The two younger colonies main- 
tained their numbers until the 22nd, after which they 
diminished till, within a few days, their tents also were 
deserted. The members of all these colonies hatched 
frorn the eggs on April 8, 9, and 10, so seven weeks is the 
greatest length of time that any of them spent on the trees 
of their birth. The caterpillar that left the tent on the 
15th came from a colony that began to hatch on April 10, 
giving an observed minimum of thirty-six days. 

After the mature caterpillars leave the tents, they 
wander at large and feed wherever they find suitable 



provender, enjoying for a while a new life free from the 
domestic routine that has bound them since the days of 
their infancy. But even their liberty has an ulterior pur- 
pose: the time is now approaching when their lives as 
caterpillars must end and the creatures must go through 
the mysteries of transformation, which, if successfully 
accomplished, will convert them into winged moths. It 
would clearly be most unwise for the caterpillars of a 
colony to undergo the period of their metamorphosis 
huddled in the remains of the tent, where some untoward 
event might bring destruction to them all. Nature has, 
therefore, implanted in the tent caterpillar a migratory 
urge, which now becomes active and leads the members of 

a family to scatter far and 

^^^^^pif£.tJ8?si^^g^^p allowed for the dispersal, 

; , J ^aPJi anc l ^en, as each wan- 

derer feels within the 
first warnings of ap- 
proaching dissolution, it 
selects a suitable place 

Fie. m. The cocoon of a tent cater- r i ■ ir • 

pillar. (Natural size) *Or inclosing Itself 111 a 


It is difficult to find many cocoons in the neighborhood 
where large numbers of caterpillars have dispersed, but 
such as may be recovered will be found among blades of 
grass, under ledges of fences, or in sheds and barns where 
they are not disturbed. The cocoon is a slender oval or 
almost spindle-shaped object, the larger ones being about 
an inch long and half an inch in width at the middle 
(Plate 14 E, Fig. 151). The structure is spun of white silk 
thread, but its walls are stiffened and colored by a yellow- 
ish substance infiltrated like starch through the meshes 
of the fabric. 

In building the cocoon the caterpillar first spins a loose 
network of threads at the place selected, and then, using 
this for a support, weaves about itself the walls of the final 



structure. On account of its large size, as compared with 
the size of the cocoon, the caterpillar is forced to double 
on itself to fit its self-imposed cell. Most of its hairs, how- 
ever, are brushed off and become interlaced with the 
threads to form a part of the cocoon fabric. When the 
spinning is finished, the caterpillar ejects a yellowish, 
pasty liquid from its intestine, which it smears all over the 
inner surface of the case; but the substance spreads 
through the meshes of the silk, where it quickly dries and 
gives the starchy stiffness to the walls of the finished 
cocoon. It readily crumbles into a yellow powder, which 
becomes dusted over the caterpillar within and floats off in 
a small yellow cloud whenever a cocoon is pulled loose 
from its attachments. 

The cocoon is the last resting place of the caterpillar. If 
the insect lives, it will come out of its prison as a moth, 
leaving the garments of the worm behind. It may, how- 
ever, be attacked by parasites that will shortly bring about 
its destruction. But even if it goes through the period of 
change successfully it must remain in the cocoon about 
three weeks. In the meantime it will be of interest to learn 
something of the structure of a caterpillar, the better to 
understand some of the details of the process of its trans- 

The Structure and Physiology of the Caterpillar 

A caterpillar is a young moth that has carried the idea 
of the independence of youth to an extreme degree, but 
which, instead of rising superior to its parents, has de- 
generated into the form of a worm. An excellent theme 
this would furnish to those who at present are bewailing 
what they believe to be a shocking tendency toward an 
excess of independence on the part of the young of the 
human species; but the moral aspect of the lesson some- 
what loses its force when we learn that this freedom of the 
caterpillar from parental restraint gives advantages to 
both young and adults and therefore results in good to 



the species as a whole. Independence entails responsibil- 
ities. A creature that leaves the beaten paths of its an- 
cestors must learn to take care of itself in a new way. And 

Fig. 152. The head of a tent caterpillar 

A, facial view. B, under surface. C, side view. Ant, antenna; Clp, clypeus; 

For, opening of back of head into body; Hphy, hypopharynx; Lb, labium; Lm> 

labrum; Md, mandible; Mx, maxilla; 0, eyes; Spt, spinneret 

this the caterpillar has 
as it has come up the 1 
possesses both instincts 

Fig. 153. The mandibles, or 
biting jaws, of the tent cater- 
pillar detached from the head 
A, front view of right mandi- 
ble. B, under side of the left 
mandible, a and p, the an- 
terior socket and posterior 
knob by which the jaw is 
hinged to the head; EMcl, 
RMcI, abductor and adductor 
muscles that move the jaw in 
a transverse plane 

learned to do preeminently well, 
ong road of evolution, till now it 
and physical organs that make it 
one of the dominant forms of in- 
sect life. 

The external organs of princi- 
pal interest in the caterpillar are 
those of the head (Fig. 152). 
These include the eyes, the an- 
tennae, the mouth, the jaws, and 
the silk-spinning instrument. A 
facial view ot a caterpillar's head 
shows two large, hemispherical 
lateral areas separated by a medi- 
an suture above and a triangular 
plate (Clp) below. The walls of 
the lateral hemispheres give at- 
tachment to the muscles that 
move the jaws, and their size is 
no index of the brain-power of 



the caterpillar, since the insect's brain occupies but a small 
part of the interior of the head (Fig. 154, Br). From the 
lower edge of the triangular facial plate (Fig. 152, Clp) is 
suspended the broad, notched front lip, or labrum (Lm) 
that hangs as a protective flap over the bases of the jaws. 
At the sides of the labrum are the very small antennae 
{Ant) of the caterpillar. On the lower part of each lateral 
hemisphere of the head are six small simple eyes, or 
ocelli (0), five in an upper group, and one near the base of 
the antenna. With all its eyes, however, the caterpillar 




Fig. 154. Diagrammatic lengthwise section of a caterpillar, showing the 

principal internal organs, except the tracheal system 

An, anus; Br, brain; Cr, crop; Ht, heart; Int, intestine; Mai, Malpighian tubule 

(two others are cut off near their bases); Mth, mouth; Qe, oesophagus; Phv, 

pharynx; Rect, rectum; SkGl, silk gland; SoeGng, suboesophageal ganglion; Vent, 

stomach, or ventriculus; VNC, ventral nerve cord 

appears to be very nearsighted and gives little evidence of 
being able to distinguish more than the presence or ab- 
sence of an object before it, or the difference between light 
and darkness. Those tent caterpillars that were starving 
on the denuded tree failed to perceive other food trees in 
lull leaf only a few feet away. 

The general external form and structure of the tent 
caterpillar is shown at A of Figure 159. The body is soft 
and cylindrical. The head is a small, hard-walled capsule 
attached to the body by a short flexible neck. Back of 
the head and neck comes first a body region consisting 
of three segments that bear each a pair of small, jointed 
legs (Z.); and then comes a long region composed of ten 
segments supported on five pairs of short, unjointed legs 



{AD, the first four pairs being on the third, fourth, fifth 
and sixth segments, and the last on the tenth segment. 
The region ot the three segments in the caterpillar bear- 
ing the jointed legs corresponds with the thorax ot an 
adult insect (Fig. 63, 77?), and that following corresponds 
with the abdomen {Ab). The thorax of the adult insect 
constitutes the locomotor center of the body, but the 
wormlike caterpillar has no special locomotor region, and 
hence its body is not separated into thorax and abdomen. 
The thoracic legs of the caterpillar terminate each in a 
single claw, but the foot of each of the abdominal legs 
has a broad sole provided with a series or circlet of claws 
and with a central vacuum cup. The abdominal legs 
of the caterpillar, therefore, are important organs of pro- 
gression, and are the chief organs of grasping or of cling- 
ing to hard or flat surfaces. 

The jaws of the caterpillar consist of a pair of large, 
strong mandibles (Fig. 152, Md) concealed, when closed, 
behind the labrum. Each jaw is hinged to the lower 
edge of the cranium at the side of the mouth by two ball- 
and-socket hinges in such a manner that, when in action, 
it swings outward and inward on a lengthwise axis. The 
cutting edges are provided with a number of strong teeth 
(Fig. 153), the points of which come together or slide 
past each other when the jaws are closed. 

The large complex organ that projects behind or below 
the mouth like a thick under lip (Fig. 152 C) is a com- 
bination of three parts that are separate in other insects. 
These are the second pair of soft jaw appendages, called 
maxillae (B, C, Mx), and the true under lip, or labium 
{Lb). The most important part of this composite struc- 
ture in the caterpillar, however, is a hollow spine (A, 
B, C, Spt) pointed downward and backward from the 
end of the labium. This is the spinneret. From it issues 
the silk thread with which the caterpillar weaves its tent 
and its cocoon. 



The fresh silk is a liquid formed in two long, tubular 
glands extending far back from the head into the body of 
the caterpillar (Fig. 1^4, SkGI). The middle part ot each 
tube is enlarged to serve as a reservoir where the silk 
liquid may accumulate (Fig. 155 A, Res); the anterior 
narrowed part constitutes the duct (Del), and the ducts 

Fig. i$$. The silk glands and spinning organs of the tent caterpillar 

A, the silk-forming organs, consisting of a pair of tubular glands (G/, G/), each 
enlarging into a reservoir {Res), and opening through a long duct (Dct) into 
the silk press (TV), with a pair of accessory glands (glands of Filippi, GIF) opening 

Into the ducts 

B, side view of the hypopharynx (Hphy) with terminal parts of right maxilla 
(Mx) and labium {Lb) attached, showing the silk press {Pr), its muscles, and 
the ducts {Dct) opening into it, and the spinneret (Spt) through which the silk is 

discharged from the press 

C, upper view of the silk press {Pr)> showing the four sets of muscles (Mcls) 

inserted on its walls and on the rod-like raphe (Rph) in its roof 

D, side view of the silk press, spinneret, raphe, and muscles 

E, cross-section of the silk press, showing its cavity, or lumen {Lum), which is 

expanded by the contraction of the muscles 



from the two glands unite in a median thick-walled sac 
known as the silk press (Pr), which opens to the exterior 
through the spinneret. Two small accessory glands, which 
look like bunches of grapes and which are sometimes 
called the glands of Filippi (Fig. 155 A, B, C, GIF), open 
into the silk ducts near their front ends. 

The relation of the silk ducts and the silk press to the 
spinneret is seen in the side view of the terminal parts of 
the labium and the left maxilla, given at B of Figure 155. 
The silk press (Pr) is apparently an organ for regulating 
the flow of the liquid silk material into the spinneret. It 

has been supposed, too, that it 
gives form and thickness to the 
thread, but the liquid material has 
still to pass through the rigid tube 
of the spinneret. 

The cut end of the press, given at 
E of Figure 15 s, shows the crescent 
form of the cavity (Lum) in cross- 
section, and the thickening in its 
roof (Rph), called the raphe. Mus- 
cles (Mcls) inserted on the raphe 
and on the sides of the press serve 
to enlarge the cavity of the press 
by lifting the infolded roof. The 
four sets of these muscles in the 
tent caterpillar are shown at C. 
The dilation of the press sucks the 
liquid silk into the cavity through 
the ducts from the reservoirs, and 
when the muscles relax, the elastic 
roof springs back and exerts a 
pressure on the silk material, which 
forces the latter through the tube 
tubules; oe, oesophagus; f tne spinneret. The continuous 

Reel, rectum; Vent, ventri- r 

cuius passageway from the ducts through 



Fig. 156. The alimentary 
canal of the tent cater- 
A, before feeding. B, after 
feeding. Cr, crop; hit, in- 
testine; Mai, Malpighian 


the press and into the spinneret is seen from the side 
at D. 

The silk liquid is gummy and adheres tightly to what- 
ever it touches, while at the same time it hardens rapidly 
and becomes a tough, inelastic thread as it is drawn out 
of the spinneret when the caterpillar swings its head away 
from the point of attachment. 

The mouth of the caterpillar lies between the jaws and 
the lips. It opens into a short gullet, or oesophagus, which, 
with the pharynx, constitutes the first part of the alimen- 
tary canal (Fig. 154, P/iy, Oe). The rest of the canal is a 
wide tube occupying most of the space within the cater- 
pillar's body and is divided into the crop {Cr), the stomach, 
or ventriculus {Vent), and the intestine [hit). The crop is 
a sac for receiving the food and varies in size according 
to the amount of food it contains (Fig. 156 A, B, Cr). 
The stomach {Vent) is the largest part of the canal. Its 
walls are loose and wrinkled when it is empty, or smooth 
and tense when it is full. The in- 
testine {Int) consists of three divi- 
sions, a short part just back of the 
stomach, a larger middle part, and a 
saclike end part called the rectum 
{Reef). Six long tubes {Mai) are 
wrapped in many coils about the in- 
testine and run forward and back in 
long loops over the rear half of the 
stomach. The three on each side Fig. 157. Crystals 
unite into a short basal tube, which fZief'of^he'^em 
opens into the first part of the intes- caterpillar, which are 

/-fi 1 1- 1 1 ejected into the walls 

tine. 1 he terminal parts of the tubes of the cocoon 

are coiled inside the muscular coat 

of the rectum. These tubes are the Malpighian tubules. 

When a tent caterpillar goes out to feed, the fore part 
of its body is soft and flabby; when it returns to the tent 
the same part is tight and firm. This is because the tent 
caterpillar carries its dinner home in its crop, digests it 



slowly while in the tent, and then goes out for more when 
the crop is empty. It is quite easy to tell by feeling one 
of these caterpillars whether it is hungry or not. The 
empty, contracted crop is a small bag contained in the 
first three segments of the body (Fig. 156 A, Cr) ; but the 
full crop stretches out to a long cylinder like a sausage, 
rilling the first six segments of the body (B, Cr), its rear 
end sunken into the stomach, and its front end pressed 
against the back of the head. 

The fresh food in the crop consists of a solt, pulpy mass 
of leaf fragments. As this is passed into the stomach, 
the crop contracts and the stomach expands, and the 
caterpillar's center of gravity is shifted backward with the 
food burden. As the stomach becomes empty there ac- 
cumulates in it a dark-brown liquid, and it becomes in- 
flated with bubbles of gas. When the caterpillar goes to 
its meals both crop and stomach are sometimes empty, 
but usually the stomach still contains some food besides 
an abundance of the brown liquid and numerous gas 
bubbles. The refuse that accumulates in the middle sec- 
tion of the intestine is subjected to pressure by the mus- 
cles of the intestinal wall, and is here molded into a pellet 
which retains the imprint of the constrictions and pouches 
of this part of the intestine and looks like a small mulberry 
when passed on into the rectum and finally extruded from 
the body. 

The alimentary canal is a tube made of a single layer 
of cells extending through the body; but its outer surface, 
that toward the body cavity, is covered by a muscle layer 
of lengthwise and crosswise fibers, which cause the move- 
ment of the food through the canal. The gullet and crop 
and the intestine are lined internally with a thin cuticula 
continuous with that covering the surface of the body, 
and these linings are shed with the body cuticula every 
time the caterpillar molts. 

The Malpighian tubules (Figs. 154, 156 A, Mai), being 
the kidneys of insects, are excretory organs that remove 



from the blood the waste products containing nitrogen, 
and discharge them into the intestine along with the waste 
parts of the food from the stomach. Ordinarily the Mal- 
pighian tubules are of a whitish color, but just before the 
tent caterpillar is ready to spin its cocoon thev become 
congested with a bright yellow substance. Under the 
microscope this is seen to consist of masses of square, 
oblong, and rod-shaped crystals (Fig. K7). At this time 
the caterpillar has ceased to feed and the alimentary canal 
contains no food or food refuse. The intestine, however, 

Fig. 1 c8. A piece of the fat-body of the fall webworm 
a, a, globules of fatty oil in the cells; Nu, Nu, nuclei of the cells 

becomes rilled with the yellow mass from the Malpighian 
tubules; and this is the material with which the tent 
caterpillar plasters the walls of its cocoon, giving them 
their yellowish color and stiffened texture. The yellow 
powder of the cocoon, therefore, consists of the crystals 
from the Malpighian tubules. 

We now come to the question of why the caterpillar eats 
so much. It is almost equivalent to asking, "Why is a 
caterpillar?" The caterpillar is the principal feeding 
stage in the insect's life; eating is its business, its reason 
for being a caterpillar. It eats not only to build up its 
own organs, many of which are to be broken down to 
furnish building material for those of the moth, but it 
eats also to store up within its body certain materials in 
excess of its own needs, which likewise will contribute to 
the growth of the moth. 

[291 ] 


The most abundant of the food reserves stored by the 
caterpillar is fat. With insects, however, fat does not 
accumulate among the muscles and beneath the skin. In- 
sects do not become "fat" in external appearance. Their 
fatty products are held in a special organ called the, fat- 

The fat tissue of a caterpillar consists of many small, 
flat, irregular masses of fat-containing cells scattered all 
through the body cavity, some of the masses adhering in 
chains and sheets forming a loose open network about the 
alimentary canal, others being distributed against the 
muscle layers and between the muscles and the body wall. 
The cells composing the tissue vary much in size and 
shape, but they are always closely adherent, and in fresh 
material it is often difficult to distinguish the cell bound- 
aries. Specimens prepared and stained for microscopic 
examination, however, show distinctly the cellular struc- 
ture (Fig. 158). Each cell contains a darkly-stained 
nucleus (Nu), but the nuclei are seen only where they lie 
in the plane of the section. The protoplasmic area about 
the nucleus in each cell appears to be occupied mostly 
with hollow cavities of various sizes (a), but in life each 
cavity contains a small globule of fatty oil. The proto- 
plasmic material between the oil globules contains also 
glycogen, or animal starch, as can be shown by staining 
with iodine. Both fat and glycogen are energy-forming 
compounds, and their presence in the fat cells of the 
caterpillar shows that the fat-body serves as a storage 
organ for these materials during the larval life. The stored 
fat and glycogen will be consumed during the period of 
metamorphosis, when the insect is deprived of the power 
of feeding and receives no further nourishment from the 
alimentary canal. The transformation processes will then 
depend upon the food materials that the caterpillar has 
stored in its own body; and the success of the pupal meta- 
morphosis will depend in large measure on the quantity 
of these food reserves. A starved caterpillar, therefore, 



is likely to be unable to accomplish its transformation, or 
it will produce a dwarfed or an imperfect adult. 

How the Caterpillar Becomes a Moth 

A short time before the caterpillar is ready to spin its 
cocoon, it ceases feeding. Its body, as we have just 
learned, contains now an abundance of energy-giving sub- 
stances stored in the cells of its fat tissue. When the work 
of constructing the cocoon is started, the alimentary canal 
is devoid of food material, the crop is contracted to a 
narrow cylinder, and the stomach is shrunken and flabby. 
The stomach, however, contains a mass of soft, orange- 
brown substance which, when examined under the micro- 
scope, is found to consist, not of plant tissue, but of animal 
cells; it is, in fact, the cellular lining of the caterpillar's 
stomach which has already been cast off into the cavity 
of the stomach. The latter is now provided with a new 
cell wall. The shedding of the old stomach wall marks the 
first stage in the dismantling of the caterpillar; it is the 
beginning of the pupal metamorphosis which will convert 
the caterpillar into the moth. The new stomach wall will 
first digest and absorb the debris of the old, in order to 
conserve its proteid materials for the constructive work 
of the pupa, and it will then itself become transformed 
into the stomach of the moth. 

After the caterpillar has shut itself into the cocoon, its 
lite as a caterpillar is almost ended. Its external appear- 
ance is already much altered by the contraction of the 
body and the loss of the hairy covering, and during the 
next three or four days a further characteristic change of 
form takes place. As the body continues to shorten, the 
first three segments become crowded together; but the 
abdomen swells out, while the abdominal legs are re- 
tracted until they all but disappear. The creature is now 
(Fig. 159 B) only half the length of the active caterpillar 
(A), and it would scarcely be recognized as the same in- 
dividual that so recently spun itself into the cocoon. 



During rhe progress of change in the external form, the 
caterpillar gradually loses the power of movement. The 
resultant inactive period in an insect's life, immediately 
preceding the visible change to the pupa, is called the 

Fig. 159. Transformation of the tent caterpillar into the moth 
[ 2 94] 


prepupal stage of the larva. The insect in the prepupal 
stage has suffered no change in external structure, it still 
wears the larval skin, and its visible difference from the 
active larva is a mere alteration in form. Internally, how- 
ever, important reconstructive processes are now taking 

The internal activities of reconstruction, which bring 
about the pupal metamorphosis of the larva to the adult, 
begin at the head end of the insect and progress poste- 
riorly. They are preceded by a loosening and subsequent 
detachment of the larval cuticula from the cellular layer 
of the skin, or epidermis, beneath it. The latter, known 
also as the hvpodermis, freed now from restraint, enters a 
period of rapid growth. On the head, the head walls are 
remodeled and take on a new form, and new antennae and 
new mouth parts are produced. The new structures have 
no regard for the forms of the old, though each is pro- 
duced from a part of the corresponding larval organ. The 
new antennae, for example, are formed from the larval 
antennae, but the antennae of the moth are to be much 
larger than those of the caterpillar. Only the tip, there- 
fore, of each new organ can be formed within the cuticular 
sheath of the old; the base pushes inward, and the elon- 
gating shaft folds against the face of the newly forming 
head. The same thing is true of the maxillae and labium, 
but in the case of the mandibles the procedure is simpler, 
for the jaws are to be reduced in the moth. The epi- 
dermal core of each mandible, therefore, simply shrinks 
within the cuticular sheath of the larval organ, leaving 
the cavity of the latter almost empty. 

As the separation of the cuticula from the epidermis 
progresses over the region of the thorax and a free space 
is created between the two layers, the wing buds, which 
heretofore have been turned inside the caterpillar's body, 
now evert and come to be external appendages of the pupal 
body though still covered by the cuticula of the larva 
(Fig. 159 C, fVi, fV 3 ). The legs of the moth pupa are 

[ 2 95] 


formed in the same way as are the antennae and the mouth 
parts, that is, they are developed from the epidermis of 
the corresponding larval legs; but, by reason of their in- 
creased size, they are forced to bend upward against the 
sides of the body of the pupa, and, when fully formed, 
each is found to have only its terminal part within the 
cuticular sheath of the leg of the caterpillar. 

From the thorax, the loosening of the cuticula spreads 
backward over the abdomen, until at last the entire insect 
lies free within the cuticular skin of the caterpillar. The 
so-called prepupal period of the caterpillar, therefore, is 
scarcely to be regarded as a truly larval stage of the in- 
sect. It is still clothed in the larval cuticula, and retains 
externally all the structural characters of the larva; but 
the creature itself is in a first growth period of the pupal 
stage, and may appropriately be designated a propupa. 

When the cuticula is separated from the epidermis all 
over the body, it may be cut open and taken off without 
injury to the wearer. The latter, now a propupa (Fig. 
159 C), is then discovered to be a thing entirely different 
in appearance from the caterpillar. It has a small head 
bent downward, a thoracic region of three segments, and 
a large abdomen. The head bears the mouth parts and a 
pair of large antennae {A)it)\ the thorax carries the wings 
{JVi, Wzi and the legs (L), which latter are much longer 
than those of the caterpillar, but, being folded beneath 
the wings, only their ends are visible in side view. The 
abdomen consists of ten segments and has lost all ves- 
tiges of the abdominal legs of the caterpillar (A, AL). 

Many important changes have taken place in the form 
and structure of the head and in the appendages about 
the mouth during the change from the caterpillar to the 
propupa, as may be seen by comparing Figure 159 H, with 
Figure 152. Most of the lateral areas of the caterpillar's 
head (Fig. 152), including the region of the six small eyes 
on each side, have been converted into the two huge eye 
areas of the pupa (Fig. 1 59 H, E), which cover the develop- 



ing compound eyes of the adult. The antennae {Ant), as 
already noted, have increased greatly in size, and they 
show evidence of their future multiple segmentation. 
The upper lip, or labrum (Lm), on the other hand, is much 
smaller in the propupa than in the caterpillar, and the 
great biting jaws of the caterpillar are reduced to mere 
rudiments in the propupa {Md), while the spinneret (Fig. 
152, Spt) is gone entirely. The labium and the two 
maxillae are longer and more distinct from each other in 
the propupa (Fig. 159 H, Lb, Mx) than in the caterpillar, 
and their parts are somewhat more simplified. The 
labium bears two prominent palpi {LbP/p). 

The remodeling in the external form of the insect pro- 
ceeds from particular groups of cells in the epidermis, 
cells that have remained inactive since the time of the 
embryo, and which, as a consequence, retain an unused 
vitality. These groups of regenerative epidermal cells, 
which are the histoblasts, or imaginal discs, of the body 
wall, have not been particularly studied in the caterpillar; 
but in certain other insects they have been found to occur 
in each segment, typically a pair of them on each side of 
the back, and a pair on each side of the ventral surface. 
At the beginning ot metamorphosis, as the larval cuticula 
separates from the epidermis, the cells of the discs multiply 
and spread trom their several centers, and the areas newly 
formed by them take on the contour and structure of the 
pupa instead of that of the larva. The old cells of the 
larval epidermis, which have reached the limits of their 
growing powers and are now in a state of senescence, give 
way before the advancing ranks of invading cells; their 
tissues go into dissolution and are absorbed into the body. 
The new epidermal areas finally meet and unite, and to- 
gether constitute the body wall of the pupa. 

While the new epidermis is giving external form to the 
pupa beneath the larval cuticula, its cells are generating 
a new pupal cuticula. As long as the latter is soft and 
plastic the cell growth may proceed, but when the cutic- 



ular substance begins to harden, growth ceases, and the 
external form of the insect will henceforth show no further 
change in its structural features. 

The propupa of the moth remains for several days a 
soft-skinned creature (Fig. 159 C) inside the cuticula of 
the larva, during which time its body contracts in size and 
its wings, legs, antennae, and maxillae lengthen. The wings 
are flattened against the sides of the body, and the other 
appendages are applied close to the under surface. Then 
a gluelike substance is exuded from the body wall, which 
fixes the members in their positions and soon dries into a 
hard coating or glaze over the body and appendages, giving 
to the whole a shell-like covering. In this way the soft 
propupa (C) becomes a chrysalis (D). Finally, the old 
caterpillar skin splits along the back of the first two body 
segments, over the top of the head, and down the right side 
of the facial triangle. The pupa now quickly wriggles out 
of the enclosing skin and pushes the latter over the rear 
extremity of its body into the end of the cocoon, where it 
remains as a shriveled mass, the last evidence of the 

The pupa, or chrysalis, of the tent caterpillar (Fig. 
159 D) is much smaller than the propupa (C), and its 
length is only about one-third that of the original cater- 
pillar (A). The color of the chrysalis is at first bright 
green on the fore parts, yellowish on the abdomen, and 
usually more or less brown on the back. Soon, however, 
the color darkens until the front parts and the wings are 
purplish black, and the abdomen purplish brown. Though 
the covering of the chrysalis is hard and rigid, the creature 
is still capable of a very active wriggling of the abdomen, 
for three of its intersegmental rings remain flexible. By 
this provision the pupa is able to divest itself of the larval 
skin. The pupae of some species of moths push them- 
selves partly out of the cocoon just before the time of 
transformation to the moth, and when the latter emerges 

[ 298 ] 


it leaves the pupal skin projecting from the mouth of the 
cocoon (Plate i 2). 

Concurrent with the remodeling in the external form of 
the insect, other changes have been taking place within the 
body. The first of the complicated metamorphic processes 
that affect the inner organs occurs in the stomach, where, 
as we have already observed, the inner wall is cast off at 
about the time that the caterpillar begins the spinning of 
its cocoon. This shedding ot the stomach lining is quite a 
different thing from the molting of an external cuticula, 
for the stomach wall is a cellular tissue. Furthermore, 
wherever other cell layers are discarded, as in the case of 
the epidermis, the cells are absorbed into the body cavity. 
A new stomach wall is generated usually from groups of 
small cells that originally lay outside the old wall and were 
retained when the latter was cast off. These cells, as do 
the imaginal discs of the epidermis, form a new lining. to 
the stomach and give a new shape to this organ, which in 
the adult insect may be quite different from that of the 
larva. The shedding of the stomach wall is not necessarily 
a part of the metamorphosis, for in some insects and in 
certain other related animals, it is said, the stomach 
epithelium as well as the cuticular lining is shed and 
renewed with each molt of the body wall. 

The parts of the alimentary canal that lie before and 
behind the stomach, that is, the oesophagus and crop 
(Fig. 154, Of, Cr) and the intestine (hit), formed in the 
embryo as ingrowths of the body wall, are regenerated 
from groups of cells in their walls in the same manner as is 
the epidermis itself, the old cells being absorbed into the 
body. The cuticular linings of these parts are shed with 
the cuticula ot the body wall at the time of the molt. The 
complete alimentary canal of the moth is very different 
from that of the caterpillar, as will be shown in the next 
section of this chapter (Fig. 164). 

The walls of the Malpighian tubules are said to be 
regenerated in some insects, but the tubules do not change 



much in form in the moth, and they continue their ex- 
cretory function during the pupal stage. The silk glands 
oi the caterpillar are greatly reduced in size, and their 
ducts, as a consequence of the suppression of the spinneret, 
open at the base of the labium within the entrance to the 

Internal organs that have not been specially modified 
in their development for the purposes of the larva, in- 
cluding usually the nervous system, the heart, the respira- 
tory tubes, and the reproductive organs, suffer little if any 
disintegration in their tissues; they simply grow to the 
mature form, which may be much more elaborate than 
that of the larva, by a resumption of the ordinary processes 
of development. The nervous system, and particularly 
the tracheal system, however, in some insects undergo 
much reconstruction between the larval and the adult 

A most important part of the reconstruction between 
the larva and the adult has to do with the muscle system. 
Since, in its two active stages, the insect leads usually 
two very different lives, the mechanism of locomotion is 
likely to be radically different in the larva and in the 
adult; and in such cases the transformation of the insect 
will involve particularly a thorough reorganization of the 
musculature. Most larvae have acquired an elaborate 
system of special muscles for their own use because they 
have adopted a wormlike mode of progression. On the 
other hand, the adults have need of certain muscles, par- 
ticularly those of the wings, which would be only an en- 
cumbrance to a larva. Consequently, muscles needed only 
by the adult are suppressed in the larval stage, and the 
special muscles of the larva must be cleared away during 
the pupal stage. The metamorphosis in the muscle sys- 
tem, therefore, varies much in different insects according 
to the mechanical difference between the larva and the 

The purely larval muscles that are to be discarded when 



their purpose has been accomplished go into a state of dis- 
solution during the pupal period. The debris of their 
tissues is thrown into the blood, from which it is later ab- 
sorbed as nutriment by the newly forming organs. The 
caterpillar has a very elaborate system of muscles forming 
a complicated network of fibers against the inner surface 
of the body wall, some running longitudinally, others 
transversely, and still others obliquely. Most of the 
transverse and oblique fibers are not retained in the moth, 
and if specimens of those muscles are examined during the 
early part of the pupal period they are seen to have a weak 
and abnormal appearance; the structure typical of healthy 
muscle tissue is obscure or indistinctly evident in them, 
and in places they are covered with groups of free oval 
cells. These cells are probably phagocvtes. 

A phagocyte is a blood corpuscle that destroys foreign 
proteid bodies in the blood, or any unhealthy tissue of the 
body. It is not probable that the insect phagocytes are 
the active cause of the destruction of the larval tissues, but 
they do engulf and digest particles of the degenerating 
tissues. They are present in large numbers in some insects 
during metamorphosis, and are scarce or lacking in others. 
The decadent state of the larval tissues that have passed 
their period of activity lays them open to the attack of 
the phagocytes, but these tissues will go into dissolution 
by the solvent powers of the blood alone. Active, healthy 
tissues are always immune from phagocytes. 

Some of the larval muscles may go over intact to the 
adult stage, and others may require only a remodeling 
or an addition of fibers to make them serviceable for the 
purposes of the adult. The adult muscles that are com- 
pletely suppressed during the larval stage appear to be 
generated anew during the pupal stage. There is a dif- 
ference of opinion among investigators as to how the new 
muscles are developed, but it is probable that they take 
their origin from the same tissues that built up the larval 


The development of the internal organs proceeds with- 
out interruption from the beginning of the propupal period 
until the adult organs are completed at the end of the pupal 
stage. The external parts, however, do not make a con- 
tinuous growth. After reaching a certain stage of de- 
velopment, the form of the body wall and of the append- 
ages is fixed by the hardening of the new cuticula on 
their outer surfaces. In this stage, therefore, they must 
remain, and the half-mature form attained is that char- 
acteristic of the pupa. The final development of the body 
wall and the appendages of the adult is accomplished by 
a second separation of the epidermis from the cuticula, 
which allows the cellular layers, now protected by the 
pupal cuticula, to go through a second period of growth 
during the pupal stage. This pupal period of growth at 
last results in the perfection of the external characters 
of the adult, which are in turn fixed by the formation of 
the adult cuticula. In the meantime, the new muscles 
that are to be retained have become anchored at their 
ends into the new cuticula, and the mechanism of the 
adult insect is ready for action. The perfect insect, 
cramped within the pupal shell, has now only to await 
the proper time for its emergence. 

Through the whole period of metamorphosis, the insect 
must depend on its internal resources for food materials. 
Oxygen it can obtain by the usual method, for its respira- 
tory system remains functional; but in the matter of 
food it is in a state of complete blockade. The pupa has 
two sources of nourishment: first, the food reserves stored 
in the cells of the fat-body; second, the materials resulting 
from the breaking down of the larval tissues, which are 
scattered in the blood and eventually absorbed. 

The fat cells, at the beginning of metamorphosis in some 
insects, give up most of their stored fat and glycogen; and 
they now become filled with small granules of proteid 
matter. The proteid granules are probably elaborated in 
the fat cells from the absorbed detritus of the larval 

[ 302 ] 


organs by means of enzymes produced in the nuclei of the 
cells. The tat cells thus take on the function of a stomach, 
converting the materials dissolved in the blood into forms 
that the growing tissues can assimilate. During this time 
the masses of fat tissue that compose the fat-body of the 





' r<- °' 

Fio. 160. Bodies in the blood of a young pupa of the tent caterpillar 

a, a free fat cell, containing large oily fat globules, and small proteid granules; 

b, <-, fat cells in dissolution; d, free proteid granules in the blood, and f, fat 

globules liberated from the disintegrating fat cells;/, blood corpuscles 

larva have broken up into free cells, and these cells, 
vacuolated with oil globules and later charged with pro- 
teid granules, now fill the blood. 

The interior of the moth pupa, or chrysalis, shortly 
after the larval skin is shed, contains a thick, yellow, 
creamy liquid. In it there may be discovered, however, 
the alimentary tract, the nervous system, and the tracheal 
tubes, the latter filled with air; but all these parts are so 
sort and delicate that they can scarcely be studied by 
ordinary methods of dissection. 

The creamy pulp of the pupa's body, when examined 
under the microscope, is seen to consist of a clear, pale, 
amber-yellowish liquid full of small bodies of various 
sizes (Fig. 160), which give it the opaque appearance and 
thick consistency. The liquid medium is the blood, or 
body lymph. The largest bodies in it are free fat cells (a); 
smaller ones are probably blood corpuscles (/); and the 



finest matter consists of great quantities of minute grains 
(d) floating about separately or adhering in irregular 
masses. Besides these elements there are many droplets 
of oil (e), recognizable by their smooth spherical outlines 
and golden-brown color. The fat cells are mostly irregu- 
larly ovoid or elliptical in shape; their protoplasm is filled 
with large and small oil globules, and contains also masses 
of fine granules like those floating free in the blood. These 
granules are the protoplasmic substances formed within the 
fat cells. Many of the cells have irregular or broken out- 
lines (b, c), as if their outer walls had been partly dis- 
solved, and the contents of such cells appear to be escap- 
ing from them. In fact, many are clearly in a state of dis- 
solution, discharging both their oil globules and their pro- 
teid inclusions into the blood; and it is clear that the 
similar matter scattered so profusely through the blood 
liquid has come from fat cells that have already disin- 
tegrated. All these materials will gradually be consumed 
in the building of the tissues of the adult, the organs of 
which are now in process of formation. 

In Chapter IV we learned that every animal consists of 
a body, or soma, formed of cells that are differentiated 
from the germ cells usually at an early stage of develop- 
ment. The function of the soma is to give the germ 
cells the best chance of accomplishing their purpose. An 
insect that goes through two active forms during its life, a 
larval and an adult form, differs from other animals in 
having a double soma. The entire organism, of course, is 
not double, for, as we have just seen in the study of the 
caterpillar, many of the more vital organs are continuous 
from the larva to the adult; but there is a group of organs 
which, after reaching a definite form of development in 
the larval stage, at the end of this stage virtually die and 
go into dissolution, while a new set of tissues develops 
into new organs or into new tissues replacing those that 
have been lost. The groups of somatic cells thatform the 
tissues and organs that undergo a metamorphosis, there- 

[3 4] 


fore, are differentiated in the embryo into two sets of cells, 
one set of which will form the special organs of the larva, 
while those of the other will remain dormant during the 
larval life to form the adult organs when the larval cells 
have completed their functions. The cells of the second 
set carry the hereditary influences that will cause them to 
develop into the original, or ancestral, form of the species; 
the cells of the first set produce the temporary larval 
form, which may retain certain primitive characters from 
the embryonic stage, but which does not represent an 
ancestral form in the evolution of the species. 

An extreme case of anything is always more easily 
understood when we can trace it back to something simple, 
or link it up with something familiar. The metamorphosis 
of insects appears to be one of the great mysteries of 
nature, but reduced to its simplest terms it becomes only 
an exaggerated case of a temporary growth in certain 
groups of cells to form something of use to the young, 
which disappears by resorption when the occasion for its 
use is past. Innumerable simple cases of this kind might 
be cited from insects; but there is a familiar case of well- 
developed metamorphosis even in our own growth, 
namely, the temporary development of the milk teeth and 
their later substitution by the adult teeth. If a similar 
process of double growth from the somatic cells had been 
carried to other organs, we ourselves should have a meta- 
morphosis entirely comparable with that of insects. 

The Moth 

For three weeks or a little longer the processes of re- 
construction go on within the pupa of the tent caterpillar, 
and then the creature that was a caterpillar breaks through 
its coverings and appears in the form and costume of a 
moth (Fig. 1^9 J). The pupal shell splits open on the 
forward part of the back (E) to allow the moth to emerge, 
but the latter then only finds itself face to face with the 
wall of the cocoon. It has left behind its cutting instru- 



ments, the mandibles, with its discarded overalls; but it 
has turned chemist and needs no tools. The glands that 
furnished the silk for the larva have shrunken in size and 
have taken on a new function; they now secrete a clear 
liquid that oozes out of the mouth of the moth and acts 
as a solvent on the adhesive surfaces of the cocoon threads. 
The strands thus moistened are soon loosened from one 
another sufficiently to allow the moth to poke its head 
through the cocoon wall and force a hole large enough to 
permit of its escape. The liquid from the mouth of the 
moth turns the silk of the cocoon brown, and the lips of 
the emergence hole are always stained the same color — 
evidence that it is this liquid that softens the silk — and 
the frayed edges of the hole left in the cocoon of the tent 
caterpillar show many loose ends of threads broken by 
the moth in its exit. 

The most conspicuous features of the moth (Fig. 16 1) 
are its furry covering of hairlike scales and its wings. 
The wings are short when the insect first emerges from 
its cocoon (Fig. 159 J), but they quickly expand to normal 
length and are then folded over the back (Fig. 161 A). 
The colors of the moths of the tent caterpillar are various 
shades of reddish-brown with two pale bands obliquely 
crossing the wings (Plate 14 G, H). The female moth 
(Plate 14 H, Fig. 161 B) is somewhat larger than the male, 
her body being a little over three-fourths of an inch in 
length, and the expanded wings one and three-fourths 
inches across. 

The tent caterpillars perform so thoroughly their duty 
of eating that the moths have little need of more food. 
Consequently the moths are not encumbered with imple- 
ments of feeding. The mandibles, which were such large 
and important organs in the caterpillar (Fig. 152, Md) 
but which shrank to a rudimentary condition in the pro- 
pupa (Fig. 159 H, Md), are gone entirely in the moth 
(Fig. 162). The maxillae, which were fairly long lobes 
in the propupa (Fig. 159 H, Mx), have likewise been 



reduced to mere rudiments in the adult, where they appear 
as two insignificant though movable knobs (Fig. 162, 
Mx). The median part of the labium has been reduced 
to almost nothing in the moth; but the labial palpi 
{LbPlp) are long and three-segmented, and when normally 
covered with hairlike scales they form two conspicuous 
leathery brushes that project in front of the face. 

The mouth parts of the tent caterpillar moth are not 
typical ot these organs of moths and butterflies in gen- 

Fig. 161. Moths ot'the tent caterpillar, Malacosoma amerhana. (A little greater 
than natural size) 

eral, for most of these insects are provided with a long 
proboscis by means of which they are able to feed on 
liquids. Everyone is familiar with the large humming- 
bird moths, or hawk moths, that are to be seen on summer 
evenings as thev dart from flower to flower, thrusting 
into each corolla a long tube uncoiled from beneath the 
head; and we have all seen the sunlight-loving butterflies 
carelessly flitting over the flower beds, alighting here and 
there on attractive blooms to sip the sweet liquid from 
the nectar cups. 

Moths and butterflies carry the proboscis tightly 
coiled, like a tiny watch spring (Fig. 163 A, Prb), be- 
neath the head and just behind the mouth. It can be 
unwound and extended (B, Prb) whenever the insect 
wants to extract a drop of nectar from the depths of a 




flower corolla, or when it 
would merely take a drink 
of water or other liquid. 
The proboscis consists oi the 
greatly lengthened maxillae 
firmly attached to each other 
by dovetailed grooves and 
ridges. The inner face of 
each maxilla is hollowed in 
the form of a groove run- 
ning its entire length, and 
the two grooves apposed 
between the united maxillae 
are converted into a central 
channel of the proboscis. 
The two blades of the pro- 
boscis spring from the sides 
of the mouth. The first 
part of the alimentary canal just back of the mouth is 
transformed into a bulblike sucking apparatus. The 


Fic. 162. Facial view of the head of 
the tent caterpillar moth, with cover- 
ing scales removed, and antennae cut 

off near their bases 
Ant, base of antenna; E, compound 
eye; Lb, labium; LbPlp, labial palpus; 
Lm, labrum; Mth, mouth; Mx, maxilla 

Fig. 163. Head and mouth parts of the peach borer moth 

A, side view. B, three-quarter facial view. Ant, basal part of antenna; E, 

compound eye; LbPlp, labial palpus; 0, ocellus; Prb, proboscis 



upper wall of the structure is ordinarily collapsed into 
the cavity of the bulb, but it is capable of being lifted by 
strong muscles inserted upon it from the walls of the 
head. The alternate opening and closing of the bulb 
sucks the liquid food up through the tube of the pro- 
boscis and forces it back into the gullet. The moths and 
butterflies are thus sucking insects, as are the aphids and 
cicadas, but they are not provided with piercing organs, 
though some species have a rasp at the end of the pro- 
boscis which is said to enable them to obtain juices from 
soft-skinned fruits. 

With the tent caterpillar, it is interesting to note, the 
maxillae are much longer in the pupa (Fig. 159 I, Mx) 
than they are in either the caterpillar or the adult moth 
(Fig. 162, A/.v), as if nature had intended the tent cater- 
pillar moth to have a proboscis like that of other moths, 
but had then changed her mind. The real meaning of 
this is that the moths of the present-day tent cater- 
pillars are descended from ancestors that had a functional 
proboscis in the adult stage like that of other moths, and 
that the reduction of the proboscis of the modern moths 
has taken place in times so recent that the organ has not 
yet been suppressed to the same degree in the pupa. 

The alimentary tract of the tent caterpillar moth is 
very different from that of the caterpillar. In the cater- 
pillar, the organ consists of three principal parts (Fig. 
164 A), the first comprising the oesophagus (Of) and the 
crop (Cr), the second being the stomach, or ventriculus 
{Vent), and the third the intestine (hit). In an adult moth 
that is almost mature, but which is still inside the pupal 
shell (B), the oesophagus has become a long narrow tube 
(Oe) at the rear end of which the crop forms a small sac 
{Cr) projecting upward, which may contain a bubble of 
gas. The stomach has contracted to a pear-shaped bag 
with very thin transparent walls, and is usually filled 
with a dark-brown liquid. The intestine has changed 
radically in form, for it now consists of a long, slender, 



tubular part, the small intestine (SInt), and of a great 
terminal receptacle, the rectum {Reef), filled with a mass 
of soft orange-colored matter. In the fully-matured insect 
(C), after it has escaped from the cocoon, still further 

Fig. 164. Transformation in the form of the alimentary canal 

of the tent caterpillar from the larva to the adult moth 
A, alimentary canal of the caterpillar. B, the same of the pupa. 

C, the same of the moth 

O, crop; /»/, intestine; Mai, Malpighian tubules (not shown full 

length); Oe, oesophagus; Reel, rectum; SInt, small intestine; Vent, 


alterations have taken place. The crop sac [Cr) is now 
greatly distended into a spherical vesicle tensely filled 
with gas — air, probably, that the moth has swallowed, 
perhaps to aid it in breaking the pupal shell, for there are 
sometimes small bubbles also in the tubular oesophagus. 

[3 IO J 


The stomach is contracted to a mere remnant of its 
former size (A, Vent), and its walls are thrown into thick 
corrugations. The intestine (Sin/) is about the same as 
in the earlier stage of the moth (B). 

Since the moth of the tent caterpillar probably eats 
nothing, it has little use for a stomach. The intestine, 
however, must serve as an outlet for the Malpighian 
tubules (Mai), since the latter remain functional through 
the pupal stage. The secretion of the tubules contains 
great numbers of minute spherical crystals, which accumu- 
late in the rectal sac (Red) where they form the orange- 
colored mass contained in this organ and discharged as 
soon as the moth leaves the cocoon. 

Most of the male moths of the tent caterpillar emerge 
from the cocoons several days in advance of the females. 
At this time their bodies contain an abundance of fat 
which fills the cells of the fat tissue as droplets of oil. 
This fat is probablv an energy-forming reserve which the 
male moth inherits from the caterpillar, for the internal 
reproductive organs are not yet fully developed and do 
not become functional until about the time the females 
are out of their cocoons. 

The bodies of the female tent caterpillar moths, on the 
other hand, contain little or no fat tissue; but each female 
is fully matured when she emerges from the cocoon, and 
her ovaries are full of ripe eggs ready to be laid as soon as 
the fertilizing element is received from the male (Fig. 165, 
Ov). The spermatozoa will be stored in a special recep- 
tacle, the spermatheca (Spm), which is connected with the 
exit duct of the ovaries (Vg) by a short tube. Each egg 
is then fertilized as it issues from the oviduct. The ma- 
terial that will form the covering of the eggs when laid is 
a clear, brown liquid contained in two great sacs (Fig. 
165, Res) that open into the end of the median oviduct 
(Vg). Each sac is the reservoir of a long tubular gland 
(CIGl). The liquid must be somehow mixed with air 
when it is discharged over the eggs to give the egg covering 



its frothy texture. It soon sets into a jellylike substance, 
then becomes firm and elastic like soft rubber, and finally 
turns dry and brittle. 

The date of the egg laying depends on the latitude of 
the region the moths inhabit, varying from the middle 

/ ! 

Sprn Bcpx Dov 

Fig. 16c. The female reproductive organs of the moth of the tent caterpillar, 

as seen from the left side 
a, external opening of the bursa copulatrix; An, anus; b, opening of the vagina; 
Bcpx, bursa copulatrix; CIG1, colleterial glands, which form the substance of the 
egg covering; Dov, duct of the left ovary; Ov, left ovary, full of ripe eggs; ov, ov, 
upper ends of the ovarian tu bules; Reel, rectum ; Res, reservoirs of the colleterial 
glands (C/GJ); Spm, spermatheca, a sac for the storage of the spermatozoa; //, 
terminal strand of the ovary; Vg, vagina 

of May in the southern States to the end of June or later 
in the north. While the eggs will not hatch until the fol- 
lowing spring, they nevertheless begin to develop at 
once, and within six weeks young caterpillars may be 
found fully formed within them (Fig. 166 B). Each little 
caterpillar has its head against the top of the shell and its 
body bent U-shaped, with the tail end turned a little to 
one side. The long hairs of the body are all turned for- 
ward and form a thin cushion about the poor creature, 
which for crimes yet uncommitted is sentenced to eight 

[3 I2 1 


months' solitary confinement in this most inhuman posi- 
tion. Yet, if artificially liberated, the prisoner takes 
no advantage of the freedom offered. Though it can 
move a little, it remains coiled (A) and will fold up again 
if forcibly straightened, thus asserting that it is more com- 
fortable than it looks. 

It is surprising that these infant caterpillars can remain 
inactive in their eggshells all through the summer, when 
the warmth spurs the vitality of other species and speeds 
them up to their most rapid growth and development. 
External conditions 
in general appear to 
have much to do with 
regulating the lives of 
insects, and if the tent 
caterpillars in their 
eggs seem to give 
proof that the crea- 
tures are not entirely 
the slaves of environ- 
ment, the truth is 
probably that all in- 
sects are not gov- 
erned by the same 
conditions. We have seen that some of the grasshoppers 
and some of the aphids will not complete their develop- 
ment except after being subjected to freezing tempera- 
tures, and so it probably is with the tent caterpillars- 
it is not warmth, but a period of cold that furnishes the 
condition necessary to the final completion of their de- 
velopment. Whatever the secret source of their 
patience, however, the young tent caterpillars will bide 
their time through all the heat of summer, the cold of 
winter, and not till the buds of the cherry or apple leaves 
are ready to open the following spring will they awake 
and gnaw through the inclosing shells against which their 
faces have been pressing all this while. 

Fig. 166. The young tent caterpillar fully 
formed within the egg by the middle of 


A, the young caterpillar removed from the 

egg. B, the caterpillar in natural position 

within the egg 


Thoughtful persons are much given to pondering on 
what is to be the outcome of our present age of intensive 
mechanical development. Thinking, the writer holds, is 
all right as a means of diverting the mind from other 
things, but those who make a practice or a profession of 
it should follow the example of that famous thinker of 
Rodin's, who has consistently preserved a most com- 
mendable silence as to the nature of his thoughts. We 
can all admire thinking in the abstract; it is the expression 
of thoughts that disturbs us. So it is that we are troubled 
when the philosophers warn us that the development of 
mechanical proficiency is not synonymous with advance- 
ment of true civilization. However, it is not for an 
entomologist to enter into a discussion of such matters, 
because an observer untrained in the study of human 
affairs is as likely as not to get the impression that only a 
very small percentage of the present human population 
of the world is devoted to efficiency in things mechanical 
or otherwise. 

There is no better piece of advice for general observance 
than that which admonishes the cobbler to stick to his 
last, and the maxim certainly implies that the entomolo- 
gist should confine himself to his insects. However, we 
can not help but remark how often parallelisms are to be 
discovered between things in the insect world and affairs 
in the human world. So, now, when we look to the insects 
tor evidence of the effect of mechanical perfection, we 
observe with somewhat of a shock that those very insect 



species which unquestionably have gone farthest along 
the road of mechanical efficiency have produced little else 
commendable. In this class we would place the mos- 
quitoes and the flies; and who will say that either mosqui- 
toes or flies have added anything to the comfort or enjoy- 
ment ot the other creatures of the world? 

Reviewing briefly the esthetic contributions of the 
major groups of insects, we find that the grasshoppers 
have produced a tribe of musicians; the sucking bugs have 
evolved the cicada; the beetles have given us the scarab, 
the glow-worm, and the firefly; the moths and butterflies 
have enriched the world with elegance and beauty; to the 
order of the wasps we are indebted for the honeybee. 
But, as for the flies, they have generated only a great 
multitude of flies, amongst which are included some of 
our most obnoxious insect pests. 

However, in nature study we do not criticize; we derive 
our satisfaction from merely knowing things as they are. 
If our subject is mosquitoes and flies, we look for that 
which is of interest in the lives and structure of these 

Flies in General 

The mosquitoes and the flies belong to tne same ento- 
mological order. That which distinguishes them princi- 
pally as an order of insects is the possession of only one 
pair of wings (Fig. 167). Entomologists, for this reason, 
call the mosquitoes and flies and all related insects the 
Diptera, a word that signifies by its Greek components 
"two wings." Since nearly all other winged insects have 
four wings, it is most probable that the ancestors of the 
winged insects, including the Diptera, had likewise two 
pairs of wings. The Diptera, therefore, are insects that 
have become specialized primarily during their evolution 
by the loss of one pair of wings. 

We shall now proceed to show that the evolution of a 
two-winged condition from one of four wings has been a 



progress toward greater efficiency in the mechanism of 
flight, and that the acme in this line has been attained by 
the flies and mosquitoes. The truth of this contention 
will become apparent when we compare the relative 
development of the wings and the manner or effective- 
ness of flight in the several principal orders of insects. 

Fig. 167. A robber fly, showing the typical structure of any 

member of the order Diptera 

The flies are two-winged insects, the hind wings being reduced 

to a pair of knobbed stalks, the halteres (HI) 

It is most probable that when insects first acquired 
wings the two pairs were alike in both size and form. 
The termites (Fig. 168 A) afford a good example of in- 
sects in which the two pairs of wings are still almost 
identical. Though the termites are poor flyers, their weak- 
ness of flight is not necessarily to be attributed to the 
form ot the wings, because their wing muscles are partially 
degenerate. The dragonflies (Fig. <;8) are particularly 
strong flyers, and with them the two pairs of wings are 
but little different in size and form; but the dragonflies 



are provided with sets of highly developed wing muscles 
which are much more effective than those of other insects. 
From these examples, therefore, we can not well judge 
of the mechanical efficiency of two pairs of equal wings 
moved by the equipment of muscles possessed by most 

Fig. i 68. Evolution of the wings of insects 
A, wings of a termite, approximately the same in size and shape. B, wings 
of a katydid, the hind wings are the principal organs of flight. C, wings of 
a beetle, the fore wings changed to protective shells, elytra (El), covering the 
hind wings. D, wings of a hawk moth, united by the spine (/), which is 
held in a hook on under surface of fore wing. E, wings of the honeybee, 
held together by hooks (h) on edge of hind wing. F, wing of a blowfly, 
and the rudimentary hind wing, or halter (HI) 

l3 l 7 


insects; but it is evident that the majority of insects 
have found it more advantageous to have the fore and 
hind wings different in one way or another. 

In the grasshoppers, it was observed (Fig. 63), the hind 
wings are expanded into broad membranous fans, while 
the fore wings are slenderer and of a leathery texture. 
The same is true of the roaches (Fig. 53), the katydids 
(Fig. [68 B), and the crickets, except in special cases where 
the fore wings are enlarged in the male to form musical 
organs (Fig. 39). In all these insects the hind wings are 
the principal organs of flight. When not in use they are 
folded over the body beneath the fore wings, which latter 
serve then as protective coverings for the more delicate 
hind wings. In the beetles (Figs. 137, 168 C) the hind 
wings are much larger than the fore wings, and, as with 
the grasshoppers and their kind, thev take the chief part 
in the function of flight. The beetles, however, have 
carried the idea of converting the fore wings into pro- 
tective shields for the hind wings a little farther than have 
the grasshoppers; with them the fore wings are usually 
hard, shell-like flaps that tit together in a straight line over 
the back (Fig. 137 A), forming a case that completely 
conceals, ordinarily, the membranous hind wings folded 
beneath them. Neither the grasshoppers nor the beetles 
are swift or particularlv efficient fivers, but thev appear to 
demonstrate that the ordinarv insect mechanism of flight 
is more effective with one pair of wings than with two. 

The butterflies and the moths use both pairs of wings 
in flight; but with these insects, it is to lie noted, the front 
wings are always the larger (Fig. 168 D). The butterflies, 
with tour broad wings, flv well in their way and are ca- 
pable of long-sustained flight, though they are compara- 
tively slow goers. Some of the moths do much better 
in the matter of speed, but it is found that the faster flying 
species have the fore wings highly developed at the ex- 
pense of the hind wings; and that the two wings on each 
side, furthermore, are yoked together in such a manner as 



to insure their acting as a single wing (D). The moths 
clearly show, therefore, as do the grasshoppers and the 
beetles, the efficiency of a single pair of flight organs as 
opposed to two. The moths, however, have attacked 
from a different angle the problem of converting their in- 
herited equipment of four wings into a two-wing mecha- 
nism — instead of suppressing the flight function in one pair 
of wings, they have given a mechanical unity to the two 
wings of each side, thus attaining functionally a two- 
winged condition. 

The wasps (Fig. 133) and bees, likewise, have evolved 
a two-winged machine from a tour-wing mechanism on the 
principle of uniting the two wings on each side. The bees 
have adopted a particularly efficient method of securing 
the wings to each other, for each hind wing is fastened to 
the wing in front of it by a series of small hooklets on its 
anterior vein that grasp a marginal thickening on the rear 
edge of the front wing (Fig. 168 E). Moreover, the bees 
have so highly perfected the unity in the design of the 
wings that only on close inspection 'is it to be seen that 
there are actually two wings on each side of the body. 

Finally, the flies, including all members of the order 
Diptera, have boldly executed the master stroke by com- 
pletely eliminating the second pair of wings from the 
mechanism of flight. The flies are literally two-winged 
insects (Figs. 167, 168 F). Remnants of the hind wings, 
it is true, persist in the form of a pair of small stalks, 
each with a swelling at the end, projecting from behind 
the bases of the wings (Figs. 167, 168 F, HI). These 
stalks are known as "balancers," or halteres, and in their 
structure they preserve certain features that show them 
to be rudiments of wings. 

The giving over of the function of flight to the front 
pair of wings has necessarily involved a reconstruction in 
the entire framework and musculature of the thorax, and a 
study of the fly thorax gives a most interesting and in- 
structive lesson in the possibilities of adaptive evolution, 

i3 l 9] 


showing how a primitive ancestral mechanism may be 
entirely remodeled to serve in a new capacity. If the flies 
had been specially "created," and not evolved, their 
structure could have been much more directly fitted to 
their needs. 

It is not only in the matter of wings and the method of 
flight that the flies show they are highly evolved insects; 


Fig. 169. The black horsefly, Tabanus atratus 

A, the entire fly. B, facial view of the head and mouth parts. Ant, antenna; 

E, E, compound eyes; Li, labium; Lm, labrum; Md, mandible; Mx, maxilla; 

MxPlp, maxillary palpus 

they are equally specialized in the structure of their mouth 
parts and in their manner of feeding. The flies subsist on 
liquid food. Those species that can satisfy their wants 
from liquids freely accessible have the mouth parts formed 
for sucking only. Unfortunately, however, as we all too 
well know, there are many species that demand, and usu- 
ally obtain, the fresh blood of mammals, including that 
of man, and such species have most efficient organs for 
piercing the skin of their victims. 

The most familiar examples of flies that "bite" are the 
mosquitoes and horseflies. The horseflies (Fig. 169 A), 
some of which are called also gadflies and deer flies, belong 
to the family Tabanidae. An examination of the head of 



the common large black horsefly (Fig. 169 B) will show 
the nature of the feeding organs with which these flies are 
equipped. Projecting downward from the lower part of 
the head are a number of appendages; these are the mouth 
parts. They correspond in number and in relative posi- 
tion with the mouth appendages of the grasshopper (Fig. 
66), but they differ from the latter very much in form 
because they are adapted to quite a different manner of 
feeding. The horsefly does not truly bite; it pierces the 
skin of its victim and sucks up the exuding blood. 

By spreading apart the various pieces that compose the 
group of mouth parts of the horsefly, it will be seen that 
there are nine of them in all. Three are median in posi- 
tion, and therefore single, but the remaining six occur in 
duplicate on the two sides, forming thus three sets of 
paired structures. The large club-shaped pieces, how- 
ever, that lie at the sides of the others, are attached at 
their bases to the second paired organs and constitute a 
part of the latter, so that there are really only two sets of 
paired organs. The anteriormost single piece is the 
labrum (Fig. 169 B, Lm)\ the first paired organs are the 
mandibles {Md)\ the second are the maxillae (Mx); the 
second median piece is the hypopharynx (not seen in 
Fig. 169 B); and the large, unpaired, hindmost organ is the 
labium (Lb). The lateral club-shaped pieces are the palpi 
of the maxillae (MxP/p). 

The labrum is a strong, broad appendage projecting 
downward from the lower edge of the face (Figs. 169 B, 
170 A, Lm). Its extremity is tapering, but the tip is 
blunt; its under surface is traversed by a median groove 
extending from the tip to the base but closed normally 
by the hypopharynx (Fig. 170 D, Hphv), which fits against 
the under side of the labrum and converts the groove into 
a tube. The upper end of this tube leads directly into the 
mouth, a small aperture situated between the base of the 
labrum and the base of the hypopharynx and opening into 
a large, stiff-walled, bulblike structure (Fig. 170 A, Pmp) 


which is the mouth cavity. The anterior wall of the bulb 
is ordinarily collapsed, but it can be lifted by a set of strong 
muscles {Mel) arising on the front wall of the head (C/p). 
This bulb is the sucking pump of the fly, and it will be 

Fig. 170. Mouth parts of a horsefly, Tabanus atratus 

A, the labrum (Lm) and mouth pump (Pmp), with dilator muscles 
of the pump {Mel) arising on the clypeal plate {Clp) of the head 

wall. The mouth is behind the base of the labrum 

B, the left mandible 

C, the left maxilla, consisting of a long piercing blade (Lc), and a 

large palpus (Pip) 

D, the labium (Lb) terminating in the large labella (La), and the 
hypopharynx (Hphy) showing the salivary duct (SID) and its 
syringe (Syr), discharging into a channel of the hypopharynx (Hphy) 

that opens at the tip of the latter 

seen that it is very similar to that of the cicada (Fig. 122, 
Pmp). In the fly, however, the liquid food is drawn up to 
the mouth through the labro-hypopharyngeal tube instead 
of through a channel between the appressed maxillae. 

The mandibles of the horsefly (Fig. 170 B, Md) are long, 
bladelike appendages, very sharp pointed, thickened on 

[3 22 ] 


the outer edges and thin on the knifelike inner edges. 
They appear to be cutting organs, for each is articulated 
to the lower rim of the head by its expanded base in such 
a manner that it can swing sidewise a little but can not be 
protruded and retracted as can the corresponding organ 
of the cicada. The maxillae (C) are slender stylets, each 
supported on a basal plate attached to the head; this plate 
carries also the large, two-segmented palpus {Pip). The 
maxillae are probably the principal piercing tools of the 
horsefly's mouth-part equipment. 

The median hypopharynx (Fig. 170 D, Hphv) is a 
tapering blade somewhat hollowed above, normally ap- 
pressed, as just observed, against the under surface of the 
labrum to form the floor of the food canal. The hypo- 
pharynx itself is traversed by a narrow tube which is a 
continuation from the salivary duct {SID). The latter, 
however, just before it enters the base of the hypopharynx, 
is enlarged to form an injection syringe {Syr). The 
salivary syringe in structure is a small replica of the mouth 
pump (A, Pmp), and its muscles arise on the back of the 
latter. The saliva of the fly is injected into the wound 
from the tip of the hypopharynx. By reason of this fact, 
the bite of a fly may be the source of infection to the 
victim, for it is evident that the injection of saliva affords 
a means for the transfer of internal disease parasites from 
one animal to another. 

Behind all the parts thus far described is the median 
labium (Fig. 170 D, Lb), a much larger organ than any of 
the others, consisting of a thick basal stalk and two great 
terminal lobes (La). The soft, membranous under sur- 
faces of the lobes, which are known as the label/a, are 
marked by the dark lines of many parallel, thick-walled 
grooves extending crosswise. These grooves may be 
channels for collecting the blood that exudes from the 
wound, or they may also distribute the saliva as it issues 
from the tip of the hypopharynx between the ends of the 
labella. The effect of the saliva of the horsefly on the 


blood is not known, but the saliva of some flies is said to 
prevent coagulation of the blood. 

Some of the smaller horseflies will give us an unsolicited 
sample of their biting powers, and in shaded places along 
roads they often make themselves most vexatious to the 
foot traveler just when he would like to sit down and enjoy 
a quiet rest. To horses, cattle, and wild mammals, how- 
ever, these flies are extremely annoying pests, and, where 
abundant, they must make the lives of animals almost 
unendurable; for the sole means of protection the latter 
have against the painful bites of the flies is a swish of the 
tail, which only drives the insects to make a fresh attack 
on some other spot. 

There is another family of "biting" flies, known as the 
robber flies, or Asilidae (Fig. 167), the members of which 
attack other insects. They are strong flyers and take their 
victims on the wing, even bees falling prey to them. The 
robber flies have no mandibles, and the strong, sharp- 
pointed hypopharynx appears to be the chief piercing 
implement. The saliva of the fly injected into the wound 
dissolves the muscles of the victim, and the predigested 
solution is then completely sucked out. 

As was shown in Chapter VIII, on metamorphosis, 
whenever the adult form of an insect is highly specialized 
for a particular kind of life, it is usually found that the 
young is also specialized but in a way of its own to adapt 
it to a manner of living quite different from that of its 
parent. This principle is particularly true of the flies, for, 
if the adult flies are to be regarded as in general the most 
highly evolved in structure of all the adult insects, there 
can be no doubt that the young fly is the most highly 
specialized of all the insect larvae. 

The flies belong to that large group of insects which do 
not have external wings in the larval stage, but with the 
flies the suppression of the body appendages includes also 
the legs, so that their larvae are not only wingless but 
legless as well (Fig. 171). The legs, however, as the wings, 

[3 2 4] 


are represented by internal buds, which, when they enter 
the period of growth during the early stage of metamor- 
phosis, are turned inside out to form the legs of the adult 


The lack of legs gives a cylindrical simplicity of form 
to most fly larvae, which not only makes these insects look 
like worms, but has caused many of them to live the life of 

Fig. 171. Structure of a fly larva, or maggot 

An, anus; ASp y anterior spiracle; DTra, dorsal tracheal trunk; LTra, lateral 

tracheal trunks; mh, mouth hooks; PSp, posterior spiracle 

a worm and to adopt the ways of a worm. In compensa- 
tion for the loss of legs, the fly larvae are provided with an 
intricate system of muscle fibers lying against the inner 
surface of the bodv wall, which enables them to stretch 
and contract and to make all manner of contortionistic 

At first thought it seems remarkable that a soft-bodied, 
wormlike creature can stretch itself by muscular contrac- 
tion. It must be remembered, however, that the body of 
the larva is filled with soft tissues, many of which are but 
loosely anchored, and that the spaces between the organs 
are filled with a body liquid. The creature is, therefore, 
capable of performing movements by making use of its 
structure as a hvdraulic mechanism; a contraction of the 
rear part of the body, for example, drives the body liquid 
and the soft movable organs forward, and thus extends the 
anterior parts of the body. A contraction of the length- 
wise muscles then pulls up the rear parts, when the move- 



ment of extension may be repeated. In this fashion the 
soft, legless larva moves forward; or, by a reversal of the 
process when occasion demands, it goes backward. 

A special feature in the construction of fly larvae is the 
arrangement of their breathing apertures, which is cor- 
related with the manner of breathing. In most insects, as 
we have learned (Fig. 70), there is a row o{ breathing pores, 
or spiracles, along each side of the body, which open into 

Fig. 172. Rat-tailed maggots, larvae of the drone fly, which live 
submerged in water or mud and breathe at the surface through a 

long, tail-like respiratory tube 
Upper figure, resting beneath a small floating object; lower, 

feeding in mud at the bottom 

lateral tracheal trunks. In the fly larva, however, these 
spiracles are closed and are not opened for respiration until 
the final change of the pupa to the adult. 

The fly larva is provided with one or two pairs of 
special breathing organs situated at the ends of the body- 
Some species have a pair of these organs at each end of the 
body (Fig. 171, ASp, PSp), and some a pair at the pos- 
terior end only. The anterior organs, when present (Fig. 
171, ASp), consist of perforated lobes on the first body 
segment, the pores of which communicate with the an- 
terior ends of a pair of large dorsal tracheal trunks {DTra). 
The posterior organs {PSp) consist of a pair of spiracles on 
the rear end of the body, which open into the posterior 
ends of the dorsal tracheae. By means of this respiratory 
arrangement, the fly larva can live submerged in water, 



or buried in mud or any other soft medium, so long as it 
keeps one end of the body out for breathing. 

The rat-tailed maggot (Fig. 172), which is the larva of 
a large fly that looks like a drone bee, has taken a special 
advantage of its respiratory system; for the rear end of its 
body, bearing the posterior spiracles, is drawn out into a 
long, slender tube. The creature, which lives in foul water 
or in mud, can by this contrivance hide itself beneath a 
floating object and breathe through its tail, the tip of 
which may come to the surface of the water at a point 
some distance away. The end of the tail is provided with 
a circlet of radiating hairs surrounding the spiracles, 
which keeps the tip of the tail afloat and prevents the 
water from entering the breathing apertures. 

The great disparity of structure between the larva of a 
fly and the adult necessarily involves much reconstruc- 
tion during the period of transformation, and probably 
the inner processes of metamorphosis are more intensive 
in the more highly specialized Diptera than in any other 
group of insects. 

The pupa of an insect, as we have seen in Chapter VIII 
(page 254), is very evidently a preliminary stage of the 
adult, the larval characters being usually discarded with 
the last molt of the larva. The pupa of most flies, however, 
while it has the general structure of the adult fly (Fig. 
182 A, F), retains the special respiratory scheme of the 
larva and at least a part of the larval breathing organs. 
The fact that the larvae breathe through special spiracles 
located on the back suggests that the primitive fly larvae 
lived in water or in soft mud, and that it was through an 
adaptation to such an environment that the lateral 
spiracles were closed and the special dorsal spiracles de- 
veloped. The retention by many fly pupae of the larval 
method of breathing and of at least a part of the larval 
respiratory organs, though their habitat would not seem 
necessarily to demand it, suggests, furthermore, that the 

[3 2 7] 


pupae of the ancestors of such species lived in the same 
medium as the larvae. , 

If our supposition is correct, we may see a reason for the 
apparent exception in the flies to the general rule that the 
pupa presents the adult structure and discards the pecu- 
liarly larval characters. The pupae of some flies whose 

9' PS P 


Fig. 173. Larva (A) and pupa (B) of a horsefly, Tabanus puncli- 

fer (about 1 yi times natural sire) 
An, anus; H, head; PSp, posterior spiracle; Sp t spiracle 

larvae live in the water, however, revert at once to the 
adult system of lateral spiracles (Fig. 173 B, Sp). With 
such species, the larva comes out of the water just before 
pupation time and transforms in some place where 
breathing is possible by the ordinary respiratory organs. 
This is the general rule with other insects whose larvae 
are aquatic. 

The order of the Diptera is a large one, and we might 
go on indefinitely describing interesting things about flies 
in general. Such a course, however, would soon fill a larger 
book than this; hence, since we are already in the last 
chapter, a more practical plan will be to select for special 
consideration a few species that have become closely as- 
sociated with the welfare of man or of his domesticated 
animals. Such species include the mosquitoes, the house 
fly, the blowfly, the stable fly, the tsetse fly, the flesh flies, 
and related forms. 




The mosquitoes, perhaps more than any other noxious 
insect, impel us to ask the impertinent question, why 
pests were made to annoy us. It would be well enough to 
answer that they were given as a test of the efficiency of 
our science in learning how to control them, if it were not 
for the other creatures, the wild animals, whose existence 
must be at times a continual torment from the bites of 
insects and from the diseases transmitted by them. Such 
creatures must endure their tortures without hope of relief, 
and there is ample evidence of the suffering that insects 
cause them. 

In earlier and more primitive days the rainwater barrel 
and the town watering trough took the place of the course 
in nature study in our present-day schools. While the 
lessons of the water barrel and the trough were perhaps 
not exact or thoroughly scientific, we at least got our 
learning from them at first hand. We all knew then what 
"wigglers" and "horsehair snakes" were; and we knew 
that the former turned into mosquitoes as surely as we 
believed that the latter came from horsehairs. Modern 
nature study has set us upon the road to more exact 
science, but the aquarium can never hold the mysteries 
of the old horse trough or the marvels of the rainwater 

The supposed ancestry of the horsehair snake is now an 
exploded myth, but the advance of science has unfortu- 
nately not altered the fact that wigglers turn into mos- 
quitoes, except in so far as the spread of applied sanita- 
tion has brought it about that fewer of them than for- 
merly succeed in doing so. And now, as we leave the 
homely objects of our first acquaintance with "wigglers" 
for the more convenient apparatus of the laboratory, we 
will call the creatures mosquito larvae, since that is what 
they are. 

The rainwater barrel never told us how those wiggling 

[3 2 9] 


mosquito larvae got into it — that was the charm of the 
barrel; we could believe that we stood face to face with the 
great mystery of the origin of life. Now, of course, we 
understand that it is a very simple matter for a female 

Fig. 174. Life stages of a mosquito, Culex quinquejasciatus 

A, the adult female. B, head of an adult male. C, a floating egg raft, with 

four eggs shown separately and more enlarged. D, a young larva suspended 

at the surface of the water. E, full-grown larva. F, the pupa resting against 

the surface film of the water 



mosquito to lay her eggs upon the surface of the water, 
and that the larvae come from the eggs. 

There are many species of mosquitoes, but, from the 
standpoint of human interest, most of them are included 
in three groups. First there are the "ordinary" mos- 
quitoes, species of the genus Culex or of related genera; 
second, the yellow- fever mosquito, Aedes aegvpti; and 
third, the malaria-carrying mosquitoes, which belong to 
the genus Anopheles. 

The common Culex mosquitoes (Fig. 174 A) lay their 
eggs in small, flat masses (C) that float on the surface of 
the water. Each egg stands on end and is stuck close to 
its neighbors in such a manner that the entire egg mass 
has the form of a miniature raft. Sometimes the eggs 
toward the margin of the raft stand a little higher, giving 
the mass a hollowed surface that perhaps decreases the 
chance of accidental submergence, though the raft is 
buoyed up from below by a film of air beneath the eggs. 

Almost any body of quiet water is acceptable to the 
Culex mosquito as a receptacle for her eggs, whether it be 
a natural pond, a pool of rainwater, or water standing in 
a barrel, a bucket, or a neglected tin can. Each egg raft 
contains two or three hundred eggs and sometimes more, 
but the largest raft seldom exceeds a fourth of an inch in 
longest diameter. The eggs hatch in a very short time, 
usually in less than twenty-four hours, though the in- 
cubation period may be prolonged in cool weather. The 
young mosquito larvae come out of the lower ends of the 
eggs, and at once begin an active life in the water. 

The body of the young mosquito larva is slender and 
the head proportionately large (Fig. 174 D). As the 
creature becomes older, however, the thoracic region of 
the body swells out until it becomes as large as the head, or 
finally a little larger (E). The head bears a pair of lateral 
eyes (Fig. 175, b), a pair of short antennae {Ant), and, on 
the ventral surface in front of the mouth, a pair of large 
brushes of hairs curved inward {a). From the sides of 

l33 l ] 


the body segments project laterally groups of long hairs, 
some of which are branched in certain species. The rear 
end of the body appears to be forked, being divided into an 

upper and a lower branch. The 
upper branch (c), however, is 
really a long tube projecting dor- 
sally and backward from the next 
to the last segment. The lower 
branch is the true terminal seg- 
ment of the body and bears the 
anal opening of the alimentary 
canal at its extremity. On the end 
of this segment four long, trans- 
parent flaps project laterally (d), 
two groups of long hairs are situ- 
ated dorsally, and a fan of hairs 
ventrally (Fig. 174 E). 

The principal characteristic of 
the mosquito larva is the speciali- 
zation of its respiratory system. 
The larva breathes through a 
single large aperture situated on 
the end of the dorsal tube that 
projects from the next to the last 
segment of the body (Fig. 175, 
PSp). This orifice opens by two 
inner spiracles into two wide 
tracheal trunks (Tra) that extend 
forward in the body and give off" 
branches to all the internal organs. 
The mosquito larva, therefore, can breathe only when the 
tip of its respiratory tube projects above the surface of the 
water, and, though an aquatic creature, it can be drowned 
by long submergence. Yet the provision for breathing at 
the surface has a distinct advantage: it renders the 
mosquito larva independent of the aeration of the water 
it inhabits, and allows a large number of larvae to thrive 

Fig. 175. Structure of a 

Culex mosquito larva 
a, mouth brushes; Ab, 
abdomen; Ant, antenna; b> 
eye; c, respiratory tube; d, 
terminal lobes; //, head; 
PSp, posterior spiracle; 
Th, thorax; Tra, dorsa 
tracheal trunks 


in a small quantity of water, provided the latter contains 
sufficient food material. 

The tip of the respiratory tube is furnished with five 
small lobes arranged like the points of a star about the 
central breathing hole. When the larva is below the sur- 
face, the points close over the aperture and prevent the 
ingress of water into the tracheae; but as soon as the tip 
of the tube comes above the surface, its points spread 
apart. Not only is the breathing aperture thus exposed, 
but the larva is enabled to remain indefinitely suspended 
from the surface film (Figs. 174 D, 181 B). In this posi- 
tion, with its head hanging downward, it feeds from a 
current of water swept toward its mouth by the vibration 
of the mouth brushes. Particles suspended in the water 
are caught on the brushes and then taken into the mouth. 
Any kind of organic matter among these particles con- 
stitutes the food of the larva. Larvae of Culex mos- 
quitoes, however, feed also at the bottom of the water, 
where food material may be more abundant. 

The body of the mosquito larva has apparently about 
the same density as water; when inactive below the sur- 
face, some larvae slowly sink, and others rise. But the 
mosquito larva is an energetic swimmer and can project 
itself in any direction through the water by snapping the 
rear half of its body from side to side, which characteristic 
performance has given it the popular name of "wiggler." 
The larva can also propel itself through the water with 
considerable speed without any motion of the body. This 
movement is produced by the action of the mouth brushes. 
Likewise, while hanging at the top of the water, the larva 
can in the same manner swipg itself about on its point of 
suspension, or glide rapidly across the surface. 

The larvae of Culex mosquitoes reach maturity in about 
a week after hatching, during the middle of summer; but 
the larval period is prolonged during the cooler seasons of 
spring and fall. The larva passes through three stages, 
and then becomes a pupa. 



The mosquito pupa (Fig. 174 F) also lives in the water, 
but is quite a different looking creature from the larva. 
The thorax, the head, the head appendages, the legs, and 
the wings are all compressed into a large oval mass from 


Fig. 176. Mouth parts of a female mosquito, Joblotia Jigilala 
A, the head with the proboscis (Prb) in natural position. B, the 
mouth parts separated, showing the component pieces of the 

Ant, antenna; E, compound eye; Hp/iy, hypopharynx; Lb, labium; 
Lm, labrum; Md, mandibles; Mx, maxillae; MxPlp, Pip, max- 
illary palpi; Prb, proboscis 

which the slender abdomen hangs downward. The pupa, 
owing to air sacs in the thorax, is lighter than water and, 
when quiet, it rises to the surface where it floats with the 
back of the thorax against the surface film. The pupa has 
lost the respiratory tube and the posterior spiracles of the 
larva, but has acquired two large, trumpetlike breathing 
tubes of its own that arise from the anterior part of the 



thorax, the mouths of which open above the water when 
the pupa comes in contact with the surface. The pupa, of 
course, does not feed, but it is almost as active as the larva, 
for it must avoid its enemies. When disturbed it rapidly 
swims downward by quick movements of the abdomen, 
the extremity of which is provided with two large swim- 
ming flaps. The duration of the pupal stage in midsummer 
is about two days. 

The adult mosquito issues from the pupal skin through a 
split in the back of the latter. We now see why the pupa 
is made lighter than 
water — it must float 
at the surface in order 
to allow the adult to 
escape into the air. 

The full-fledged 
mosquito (Fig. 174 A) 
has the general fea- 
tures of any other 
two-winged fly, but 
it is distinguished 
from nearly all other 
flies by the presence 
of scales on its wings 
and on parts of its 
head, body, and ap- 
pendages. The mouth 
parts of the adult 
mosquito are of the 
piercing and sucking type, and are similar in structure to 
those of the horsefly, except that the individual pieces are 
longer and slenderer, and together constitute a beak, 
or proboscis, extending forward and downward from the 
head (Fig. 176 A, Prb). The male and the female mos- 
quitoes are readily distinguishable by the character of the 
antennae, these organs in the male being large and 
feathery (Fig. 174 B), while those of the female are 

I 335} 

Fig. 177. A'edes airopalpus, male, a mosquito re- 
lated to the yellow fever mosquito and similar to 
it in appearance 


threadlike and provided with comparatively few short 
hairs (A). The sexes differ also in the mouth parts, for, 
as in the horseflies, the males lack mandibles. 

The mouth parts of the mosquito, in the natural posi- 
tion, do not appear as separate pieces, as do those of the 
horsefly. The various elements, except the palpi, are com- 
pressed into a beak that projects forward and downward 
from the lower part of the head (Fig. 176 A, Prb). The 
length of the beak varies in different kinds of mosquitoes; 
it is particularly long in the large South American species 
shown in Figure 176. 

When the beak of the female mosquito is dissected 
(Fig. 176 B), the same equipment of parts is revealed as is 
possessed by the female horsefly (Fig. 169 B), namely, a 
labrum (Lm), two mandibles (\ld), two maxillae (Mx), a 
hypopharynx (Hphv), and a labium (Lb). It is the labium 
that forms most of the visible part of the beak, the other 
pieces being concealed within a deep groove in its upper 

The labrum (Pig. 176 B, Lm) is a long median blade, 
concave below, terminating in a hard, sharp point; it is 
probably the principal piercing tool of the mosquito's 
outfit. The mandibles of the mosquito (Md) are very 
slender, delicate bristles; those of the species figured are 
so weak that it would seem they can be of little use to the 
insect. The maxillae (Mx) are thin, flat organs with 
thickened bases, each terminating in a sharp point armed 
on its outer edge with a row of backward-pointing, saw- 
like teeth which probably serve to keep the mouth 
parts fixed in the puncture as the piercing labrum is 
thrust deeper into the flesh. The palpi (MxPlp) arise 
from the bases of the maxillae. The hypopharynx (Hphv) 
is a slender blade with a median rib which is traversed by 
the channel of the salivary duct. Its upper surface is con- 
cave and, in the natural position, is closed against the 
concave lower side of the labrum, the two apposed pieces 
thus forming between them a tube which leads up to the 



mouth opening. The saliva of the mosquito is injected 
into the wound from the tip of the hypopharynx, and the 
blood of the victim is sucked up to the mouth through the 
labro-hypopharyngeal tube. The labium (Lb) serves 

Fig. 178. Mosquito larvae 
A, Aedes atropalpus. B, Anopheles pitnctipennis, the 

malaria mosquito larva 

c, respiratory tube; d, terminal lobes; e, stellate groups 

of hairs that hold the larva at the surface of the water 

(fig. 181 A); /, spiracular area; PSp, spiracle 

principally as a sheath for the other organs. It ends in 
two small lateral lobes, the labella, between which pro- 
jects a weak, median tonguelike process. When the mos- 
quito pierces its victim the base of the labium bends back- 
ward as the other bristlelike members of the group of 
mouth parts sink into the wound. 

Mosquitoes of both sexes are said to feed on the sap of 



plants, which they extract by puncturing the plant tissues; 
they will also feed on the exuding juices of fruit, or on any 
soft vegetable matter. The females, however, are notori- 
ous for their propensity for animal blood, and they by no 
means limit their quest for this article of food to human 
beings. The male mosquitoes, apparently, very rarely 
depart from a vegetarian diet. The pain from the bite of 
a female mosquito and the subsequent irritation and 
swelling probably result from the injection of the secre- 
tion from the salivary glands of the insect into the wound. 
It is said that the saliva of the mosquito prevents coagula- 
tion ot the blood. 

Because ot the short time necessary for the completion 
of the life cycle from egg to adult during summer, there 
are many generations ot mosquitoes trom spring to tall. 
The winter is passed both in the adult and in the larval 
stage. Fertile females may survive cold weather in pro- 
tected places; and larvae found in large numbers, frozen 
solid in the ice of ponds, have become active on being 
thawed out, and capable of development when given a 
sufficient degree of warmth. 

The yellow-fever mosquito, now known as Aedes aegypti 
but at the time of the discovery of its relation to yellow 
fever generally called Stegomvia fasciata, is similar in its 
habits during the larval and pupal stages to the Culex 
mosquitoes. It lays its eggs singly, however, and they 
float unattached on the surface of the water. The adult 
mosquito may be identified by its decorative markings. 
On the back of the thorax is a lyrelike design in white on a 
black ground; the joints of the legs are ringed with white; 
the black abdomen is conspicuously cross-banded with 
white on the basal half ot each segment. The male has 
large plumose antennae and long maxillary palpi. The 
female has a strong beak, but small palpi, and her an- 
tennae are of the short-haired form usual with female 
mosquitoes. The species of Aedes shown in Figure 177 
much resembles the yellow-fever mosquito, but it is a 

[ 33* \ 


more northern one common about Washington, D. C, 
where it breeds in rock pools along the Potomac River. 

The larva of Aedes (Fig. 178 A) resembles a Culex larva, 
but it feeds more habitually at the bottom of the water 
and may spend long periods below without coming to the 

Fig. 179. Mosquito pupae in natural position resting against the under 

surface of the water 

A, Aedes atropalpus. B, Anopheles punclipennis 

surface for air. In its search for food it noses about in the 
refuse at the bottom of the water and voraciously con- 
sumes dead insects and small crustaceans. The pupa like- 
wise (Fig. 179 A) does not differ materially from a Culex 
pupa. When quiet it floats at the surface of the water 
with the entire back of its thorax against the surface film 
and the tips of its breathing tubes above the surface. 
Probably no mosquito pupa hangs suspended from its 
respiratory tubes in the manner in which the pupae of 
various species are often figured. 

Aedes aegypti is the only known natural carrier of the 
virus of yellow fever from one person to another. The 
disease can be taken only from the bite of a mosquito of 
this species that has become infected by previous feeding 
on the blood of a yellow-fever patient. The organism 
that produces yellow fever is perhaps not yet definitely 
known, though strong evidence has been adduced to show 



that it is one of the minute, non-filterable organisms 
called spirochetes. The virus will not develop in the 
mosquitoes at a temperature below 68° F., and A'edes 

aegvpti will not breed 
y in latitudes much be- 

/ yond the possible 

range of yellow fever. 
Yellow fever, there- 
fore, is a disease ordi- 
narily confined to the 
tropics and warmer 
parts of the temper- 
ate zones. Season- 
al outbreaks of it 
that have occurred in 
northern cities have 
been caused probably 
by local infestations 
of infected mosqui- 
toes brought in on 
ships from some 
southern port. 

The malaria mos- 
quitoes belong to the genus Anopheles, a genus repre- 
sented by species in most temperate and tropical regions 
of the world, which are prevalent wherever malaria oc- 
curs. Our most common malaria species is Anopheles 
punctipennis (Fig. 180), characterized by a pair of dull 
white spots on the edges of the wings. The Anopheles 
females lay their eggs singly on the surface of the water, 
where they float, each buoyed up by an air jacket about 
its middle. 

The larvae of Anopheles (Fig. 178 B) differ conspicu- 
ously from those of Culex and Aedes both in structure and 
habits. Instead of a respiratory tube projecting from near 
the end of the body, as in Culex (Figs. 174 E, 17O) there 
is a concave disc (Fig. 178 B,/) on the back of the next to 



180. The female malaria mosquito, 
Anopheles punctipennis 


the last segment, in which the posterior spiracles (PSp) 
are located. The larva floats in a horizontal position just 
below the surface film of the water (Fig. 1 8 1 A), from 
which it is suspended by a series of floats (Fig. 178 B, e) 
consisting of starlike groups of short hairs arranged in 
pairs along the back. The spreading tips of the hairs pro- 


Fig. 181. Feeding positions of Anopheles and Culex mosquito larvae 
A, Anopheles larva suspended horizontally beneath the surface film, and feeding 
at the surface with its head inverted. B, Culex larva hanging from the respira- 
tory tube 

ject slightly above the water surface and keep the larva 
afloat. In the floating position, the respiratory disc 
breaks through the surface film, and its raised edges leave 
a dry area surrounding the spiracles. The long hairs that 
project from the sides of the thorax and the first three 
body segments are mostly branched and plumose. 

The Anopheles larva (Fig. 181 A) feeds habitually at 
the top of the water. When disturbed it shoots rapidly 
across the surface in any direction, but goes downward 
reluctantly. In order to feed in its horizontal position, 
it turns its head completely upside down and with its 
mouth brushes creates a surface current toward its mouth. 

The pupa of Anopheles (Fig. 179 B) is not essentially 



different from that of Culex or Aedes. Its most distinc- 
tive character is in the shape of the respiratory tubes, 
which are very broad at the ends. 

The parasite of malaria is not a bacterium but a micro- 
scopic protozoan animal named Plasmodium. There are 
several species or varieties that correspond with the differ- 
ent varieties of the disease. The malaria Plasmodium has 
a complicated life cycle and is able to complete its life only 
when it can spend a part of it in the body of a mosquito 
and the other part in some vertebrate animal. In the 
human body the malaria parasites live in the red corpus- 
cles of the blood. Here they multiply by asexual repro- 
duction, producing for a while many other asexual gener- 
ations. Eventually, however, certain individuals are 
formed that, if taken into the stomach of an Anopheles 
mosquito, develop there into males and females. In the 
stomach of the mosquito, these sexual individuals unite 
in pairs, and the resulting zygotes, as they are called, 
penetrate into the cells of the stomach wall. Here they 
live for a while and multiply into a great number of small 
spindle-shaped creatures, which go through the stomach 
wall into the body cavity of the mosquito and at last col- 
lect in the salivary glands. If now the mosquito, with its 
salivary glands full of the Plasmodium parasites in this 
stage, bites some other animal, the parasites are almost 
sure to be injected into the wound with the saliva. If 
they are not at once destroyed by the white blood cor- 
puscles, they will quick] v enter the red blood corpuscles, 
and the victim will soon show symptoms of malaria. 

The House Fly and Some of Its Relations 

Our familiar domestic pest, the house fly, may be taken 
as the type of a large group of flies, and in particular of 
those belonging to the family Muscidae, which is named 
from its best known member, Musca domestica, the house 
fly — musca being the Latin word for fly. 

The house fly (Fig- 182 A), though particularlv a domes- 



tic pest to people that live indoors, is intimately associated 
with the stable. Its favorite breeding place is the manure 
pile. Here the female fly lays her eggs (B), and here the 
larvae, or maggots (C), live until they are ready for trans- 
formation. It is estimated that fully ninety-five per 
cent of our house flies have been bred in horse manure. 
A few may come from garbage cans, or from heaps of 
vegetable refuse, but such sources of fly infestation are 
comparatively unimportant. Measures of fly control are 
directed chiefly to preventing the access of flies to stable 
manure and the destruction of maggots living in it. 

The eggs of the house fly (Fig. 182 B) are small, white, 
elongate-oval objects, about one twenty-fifth of an inch 
in length, each slightly curved on one side and concave on 
the other. The female fly begins to lay eggs in about ten 
days after having transformed to the adult form, and she 
deposits from 75 to 150 eggs at a single laying. She re- 
peats the laying, however, at intervals during her short 
productive period of about twenty days, and in all may 
deposit over 2,000 eggs. Each egg hatches in twenty-four 
hours or less. 

The larva of the house fly, in common with that of many 
other related flies, is a particularly wormlike creature, and 
is commonly called a maggot (Fig. 182 D). Its slender 
white body is segmented, but, in external appearance, it 
is legless and headless. On a flat area at the rear end of 
the body are located two large spiracles (PSp), which 
the novice might mistake for eyes. The tapering end of 
the body is the head end, but the true head of the maggot 
is withdrawn entirely into the body. From the aperture 
where the head has disappeared, which serves the maggot 
as a mouth, two clawlike hooks project (mh), and these 
hooks are both jaws and grasping organs to the maggot. 
The larva sheds its skin twice during the active part of its 
life, which is very short, usually only two or three weeks. 
Then it crawls off to a secluded place, generally in the earth 
beneath its manure pile, where it enters a resting condi- 



tion. Its skin now hardens and contracts until the 
creature takes on the form of a small, hard-shelled, oval 
capsule, called a puparium (Fig. 182 E). 

Fig. 182. The house fly, Musca domestica 

A, the adult fly (5 % times natural size). B, the house fly egg (greatly magnified). 

C, larvae, or maggots, in manure. D, a larva (more enlarged). E, the puparium, 

or hardened larval skin which becomes a case in which the larva changes to a 

pupa. F, the pupa 

I 344] 


Within the puparium, the larva sheds another skin, and 
then transforms to the pupa. The pupa (Fig. 182 F) is 
thus protected during its transformation to the adult by 
the puparial skin of the larva, which serves in place of a 
cocoon. When the adult is fully formed, it pushes off a 
circular cap from the anterior end of its case, and the fly 
emerges. The length ot the entire cycle from egg to adult 
varies according to temperature conditions, but it is 
usually from twelve to fourteen days. The adult flies are 
short-lived in summer, thirty days, or not more than two 
months, being their usual span of life. In cooler weather, 
however, when their activities are suppressed, they live 
longer, and a few survive the winter in protected places. 

One of the essential differences between flies of the 
house fly type and the mosquitoes and horseflies is in the 
structure of the mouth parts. The house fly lacks mandi- 
bles and maxillae, but it retains the median members of 
the normal group of mouth-part pieces, which are the 
labrum, the hypopharynx, and the labium. These parts 
are combined to form a sucking proboscis that is ordi- 
narily folded beneath the head, but which is extended 
downward when in use (Fig. 183 A, Prb). 

The labium (Fig. 183 B, Lb) is the principal component 
ot the proboscis of the house fly, and its terminal lobes, or 
labella {La), are particularly well developed. From the 
base ot the labium there projects forward a pair of palps 
(Pip), which are probably the palpi of the maxillae, 
though those organs are otherwise lacking. The anterior 
surface of the labium is deeply concave, but its trough- 
like hollow is closed by the labrum (Lm). Against the 
labial wall of the inclosed channel lies the hypopharynx 
(Hphy). When the lobes of the labium are spread out, the 
anterior cleft between them is closed except for a small 
central aperture {a). This opening becomes the func- 
tional mouth of the fly, though the true mouth is situated, 
as in other insects, between the bases of the labrum and 
the hypopharynx, and opens into a large sucking pump 



having the same essential structure as that of the horse- 
fly (Fig. 170 A). 

The house fly has no piercing organs; it subsists en- 
tirely on a liquid diet. The food liquid enters the aper- 
ture between the labella, and is drawn up to the true 






Fig. 183. Head and mouth parts of the house fly 

A, lateral view of the head with the proboscis (Prb) extended. Ant, 
antenna; E, compound eye; La, labella, terminal lobes of the pro- 
boscis; Pip, maxillary palpi (the maxillae are lacking); Prb, pro- 

B, the proboscis of the fly, as seen in three-quarter front view and 
from below. The proboscis consists of the thick labium (Lb), ending 
in the labellar lobes (La), between which is a small pore (a) leading 
into the food canal (FC) of the proboscis. The food canal contains 
the hypopharynx (Hphy), and is closed in front by the labrum (Lm) 

mouth through the food canal in the labium between the 
labrum and the hypopharynx. The fly, however, is not 
dependent on natural liquids; it can dissolve soluble sub- 
stances, such as sugar, by means of its saliva. The 
saliva is ejected from the tip of the hypopharynx, and 
probably spreads over the food through the channels of 
the labial lobes. These same channels, perhaps, also 
collect the food solution and convey it to the labellar 



During recent years we have become so well educated 
concerning the ways of the house fly, its disgusting habits 
of promiscuous feeding, now in the garbage can or some- 
where worse, and next at our table or on the baby's face, 
and we have learned so much about its menace as a pos- 
sible carrier of disease, that it is scarcely necessary to en- 
large here upon the fly's undesirability as a domestic 

The most serious accusation against the house fly is 
that, owing to the many kinds of places it frequents with- 
out regard to sanitary conditions, and to its indiscriminate 
feeding habits, there is always a chance of its feet, body, 
mouth parts, and alimentary canal being contaminated 
with the germs of disease, particularly those of typhoid 
fever, tuberculosis, and dysentery. It has been demon- 
strated that flies can carry germs about with them which 
will grow when given a proper 
medium, and likewise that 
flies taken at large may be 
covered with bacteria, a 
single fly sometimes being 
loaded with millions of them. 
The wisdom of sanitary 
measures for the protection 
of food from contamination 
by flies can not, therefore, 
be questioned. 

There is one form of insect 
villainy, however, of which 
the house fly is not guilty; 
the structure of its mouth 
parts clears it of all accusa- 
tions of biting. And yet we 
hear it often asserted by per- 
sons of unquestioned veracity that they have been bitten 
by house flies. The case is one of mistaken identification 
and not of imagination on the part of the plaintiff; the 


Fig. 184. Head of the stable fly, 
Stomoxys calci trans 

Ant y antenna; Pfp> maxillary pal- 
pus; Prb y proboscis 


insect that inflicts the bite is not the house fly, but another 
species closely resembling the common domestic fly in gen- 
eral appearance, though a little smaller. If the culprit is 
caught, there may be seen projecting from its head a long, 
hard, tapering beak (Fig. 184, Prb), an organ quite differ- 
ent from any part of the mouth equipment of the true 
house fly (Fig. 183). This biting fly is, in fact, the stable 
Jlv, a species known to entomologists as Stomoxys calci- 
trans. It belongs to the same family as the house fly, and 
while it sometimes comes about houses, it is particularly 
a pest of horses and cattle. 

The stable fly lives in most parts of the inhabited world. 
Both sexes have blood-sucking habits, and probably feed 
on any kind of warm-blooded animal, though the species 
is most familiar as a frequenter of stables and as a pest 
of domestic stock. The stable fly breeds mostly in fer- 
menting vegetable matter, the larvae being found prin- 
cipally under piles of wet straw, hay, alfalfa, grain, weeds, 
or any vegetable refuse. 

Cattle are afflicted by another pestiferous fly called 
the horn fly, or Haematobia irritans. The species gets its 
common name from the fact that it is usually observed 
about the bases of the horns of cattle, where great numbers 
of individuals often assemble. But the horns of the 
animals are merely convenient resting places. Haematobia 
is a biting fly like Stomoxys, and, because of its greater 
numbers, it often becomes a most serious pest of cattle. 
Through irritation and annoyance during feeding, it may 
cause loss of flesh in grazing stock, and a reduction of milk 
in dairy cows. The horn fly resembles the stable fly, but is 
smaller, being about one-half the size of the house fly. It 
breeds mostly in fresh manure of cattle dropped in the 

Of all the biting flies there is none to compare with 
the tsetse fly of Africa (Fig. 185). Not only is this fly an 
intolerable nuisance to men and animals because of the 
severity of its bite, but it is a deadly menace by reason of 



its being the carrier of the parasite of African sleeping 
sickness of man, and that of the related disease called 
nagana in horses and cattle. 

African sleeping sickness is caused by a protozoan para- 
site of the genus Trypanosoma that lives in the blood and 
other body liquids. Trypanosomes are active, one-celled 
organisms having one end of the body prolonged into a 
tail, or flagellum. They are found as parasites in many 
vertebrate animals, but most of them do not produce dis- 
ease conditions. There are at least three African species, 
however, whose presence in the blood of their hosts means 
almost certain death. Two cause the sleeping sickness in 
man, and the other produces nagana in horses, mules, and 
cattle. The two human species have different distribu- 
tions and produce each a distinct variety of the disease. 
One is confined to the tropical 
parts of Africa, the other is 
more southern. The southern 
form of the disease is said to be 
much more severe than the 
tropical form, claiming its vic- 
tims in a matter of months, 
while the other may drag along 
for years. The sleeping sick- 
ness and nagana trypanosomes 
are entirely dependent in nature 
on the tsetse flies for their 
means of transport from one 
person or from one animal to 

The tsetse fly (Fig. 185) is a 
larger relation of the horn fly 
and the stable fly, having the same type of beak and an 
insatiable appetite for blood. The tsetse fly genus is 
Glossina. There are two species particularly concerned 
with the transportation of sleeping sickness, corresponding 
with the two species of trypanosomes that cause the two 


Fig. 185. A tsetse fly, Glossina 

palpalis, male (about five times 

natural size) 


forms of the disease. One is Glossina palpalis (Fig. 185), 
distributor of the tropical variety of the disease; the other 
is Glossina morsitans, carrier both of the southern variety 
of sleeping sickness and of nagana. 

The stable fly, the horn fly, and the tsetse fly, we have 
said, belong to the same family as the house fly, namely, 
the Muscidae; and yet they appear to have mouth parts of 
a very different type. The differences, however, are of a 
superficial nature. All the muscid flies, biting and non- 
biting, have the same mouth-part pieces, which are the 
labrum (Figs. 183 B, 186 C, Lm), the hypopharynx 
(Hphy), and the labium {Lb). They lack, mandibles and 
maxillae, though the maxillary palps {Pip) are retained. 
In the biting species, the labium is drawn out into a long, 
slender rod (Fig. 186 C, Lb), and its terminal lobes, the 
labella {La), are reduced to a pair of small, sharp-edged 
plates armed on their inner surfaces with teeth and ridges. 
In the natural position, the deflected edges of the labrum 
(Fig. 186 B, Lm) are held securely within the hollow of the 
upper surface of the labium {Lb), the two parts thus in- 
closing between them a large food canal {FC) at the bot- 
tom of which lies the slender hypopharynx (Hphy), con- 
taining the exit tube of the salivary duct. 

The biting muscids, therefore, have a strong, rigid, 
beaklike proboscis formed of the same pieces that com- 
pose the sucking proboscis of the house fly (compare 
Fig. 183 A with Figs. 184 and 186 A), but the labium is so 
modified that it becomes an effective piercing organ. When 
one of these flies bites, it sinks the entire beak into the flesh 
of its victims. The tsetse fly is said to spread its front legs 
apart when it alights for the purpose of feeding, and to 
insert its beak by several quick downward thrusts of the 
head and thorax. The insect then quickly fills itself with 
blood, with which it may become so distended that it can 
scarcely fly. The bulb at the base of the tsetse fly's 
labium (Fig. 186 C, b) is no part of the sucking apparatus; 
it is merely an enlargement for the accommodation of 



muscles. The true sucking organ lies within the head 
(Pmp), and does not differ in structure from that of other 

While our indictment of the flies has applied thus far 
only to the insects in the mature form, there are species 
which, though entirely innocent of any criminality in their 


Fie. 186. Head and mouth parts of the tsetse fly, Gloisina 

A, lateral view of the head and proboscis (Prb) of Glossina palpalis, 


B, cross-section of the proboscis of Glossina fusca (from Vogel), 
showing the food canal (FC) inclosed by the labrum {Lm) and 
labium (Lb), and containing the tubular hypopharynx (Hphv) 

through which the saliva is injected into the wound 

C, mouth parts of Glossina palpalis, with the parts of the proboscis 
separated. b, basal swelling of the labium; La, the labella, or 
terminal lobes of the labium used for cutting into the skin of the 
victim; Lb, labium; Lm, labrum; Pip, maxillary palpus (the 

maxillae are lacking); Pmp, mouth pump 



adult behavior, are, however, most obnoxious creatures 
during their larval stages. The ordinary blowflies, which 
are related to the house fly, lay their eggs in the bodies of 
dead animals, where the larvae speedily hatch and feed 
on the putrefying flesh. Another kind of blowfly deposits 
living larvae instead of eggs. These flies may be regarded 
as beneficial in that their larvae are scavengers. But some 
of their relations appear to have taken a diabolical hint 
from their habits, for they make a practice of depositing 
their eggs in open wounds, sores, or in the nostrils of living 
animals, including man. The larvae burrow into the tis- 
sues of the victims and cause extreme annoyance, suffer- 
ing, and even death. A notable species of this class of 
pests is the screw worm. Infestation by fly larvae, or 
maggots, is called myiasis. 

Well-known cases of animal myiasis are that of the bot- 
fly in horses and of the ox warble in cattle. The flies of 
both these species lay their eggs on the outside of the 
animals. The young larvae of the botfly are licked off 
and swallowed, and then live until full-grown in the 
stomach of the host. The young ox-warble larva burrows 
into the flesh of its host and lives in the body tissues until 
mature, when it bores through the skin on the back of the 
afflicted beast, drops out, and completes its transforma- 
tion in the ground. 

Not only animals but plants as well are subject to in- 
ternal parasitism by fly larvae. Garden crops are at- 
tacked by leaf maggots and root maggots; orchardists in 
the northern States have to contend against the apple 
maggot, which is a relation of the olive fly of southern 
Europe and of the destructive fruit flies of tropical coun- 
tries. That notorious scourge of wheat fields, the Hessian 
fly, is a second or third cousin of the mosquito, and it is in 
its larva form that it makes all the trouble. 

The special attention that has been given to pestiferous 
flies must make it appear that the Diptera are a most 
undesirable order of insects. As a matter of fact, however, 



there are thousands of species of flies that do not affect us 
in any injurious way; while, furthermore, there are 
species, and many of them, that render us a positive serv- 
ice by the fact that their larvae live as parasites in the 
bodies of other injurious insects and bring about the de- 
struction of large numbers of the latter. 

Scientifically, the Diptera are most interesting insects, 
because they illustrate more abundantly than do the 
members of any other order the steps by which nature has 
achieved evolution in animal forms. An entomologist 
would say that the Diptera are highly specialized insects; 
and as evidence of this statement he would point out that 
the flies have developed the mechanical possibilities of 
the common insect mechanism to the highest general level 
of efficiency attained by any insect and that they have 
carried out many lines of special modification, giving a 
great variety of new uses for structures originally limited 
to one mode of action. But when we say that any animal 
has developed to this or that point of perfection, we do not 
mean just what we say, for the creature itself has been 
the passive subject of influences working upon it or within 
it. A fundamental study of biology in the future will 
consist of an attempt to discover the forces that bring 
about evolution in living things. 



Acrididae, 28 
Aedes, adult, 338 
larva, 339 

pupa, 339 
Aedes aegypti, 331, 339, 340 

carrier of yellow fever, 339 
Aesop and the cicada, 183 
Agile meadow grasshopper, 53 
Alimentary canal, 109 
Amblycorypha oblongifolia, 39 

habits, 40 

song, 41 

A me collective, 143 
American cockroach, 79 
Anabrus simplex, 54 
Ancient insects, 77 
Angular-winged katydids, 41-43 
Annual cicadas, 184 

song, 184 
Anopheles, 331, 340 

punctipennis, see Malaria mos- 
Antennae, 12 
Aphids, 152 

apple, 157, 162 

birth, 164 

cornicles, 174 

eggs, 157 
feeding, 153 
garden, 171, 172 
hatching, 159-161 
mouth parts, 153 
parasites, 178 
predators, 175 
stem mothers, 162 
wing production, 164-166 
young, 162 

Aphis, 153 

apple-grain, 170 

green apple, 162 

rosy apple, 168 
Aphis-lion, 176 
Arthropoda, 26 
Asilidae, 324 
Australian cockroach, 79 


Beetles, blister, 22-25 

lady, 175, 230 

May, 230 

young, 237 
Behavior, 126 
Black cricket, 60 

in New England, 60 

rivalry of males, 62 

song, 60-63 
Black-horned tree cricket, 67 

antennal marks, 67 

attraction of female by male, 

song, 68 
Blatella germanica, see German 

Blood of insects, 1 12 
Blowflies, 352 
Botflies, 352 
Brain, 117, 118 
Broad-winged tree cricket, 65 

antennal marks, 67 

song, 64 
Bush crickets, 69 

song, 70 
Bush katydids, 38 

song, 39 



Camel crickets, 55 
Cantharidin, 23 
Carboniferous dragonflies, 95 

insects, 86, 89, 90 

plants, 87, 88 
Caterpillar, 262 

alimentary canal, 289, 290 

celery, 229 

jaws, 286 

life, 262 

nature, 228 

silk glands, 287 
press, 288 

spinneret, 286 

spinning of cocoon, 282, 283 

structure, 237 

tent, 262-293 

transformation to moth, 293-305 
Caterpillar and moth, 262 
Cecropia moth, 228, 229 
Cellulose, digestion of, by ter- 
mites, 137 
Chitin 256 
Chloealtis conspersa, 30 

musical apparatus, 30 

song, 30, 31 
Chrysalides, 251 
Cicadas, 182 

annual, 184 

periodical, 184-225 
Cicadidae, 182 
Circotettix carlingianus, 32 

verruculatus, 32 
Cockroaches, 79 
Collembola, 247 
Common meadow grasshopper, 52 

song, 53 
Coneheads, 50 
Conocephalus fasciatus, 54 

song, 54 
Corn-root aphis, 172 
Coulee cricket, 54 

Cricket family, 55 
Crickets, 55 

bush, 69 

camel, 55 

European, 55 

field, 58 

foot, 55 

mole, 58 

musical organs, 56, 57 

tree, 63 
Croton bug, see German roach 
Culex, 331 

eggs, 33 1 

food, 337, 338 

larva, 33 1 

male and female, 33^ 

mouth parts, 335-337 

Deer flies, 320 
Diapheromerafemorata, 71 
Digestion, 1 10 
Diptera, 315 
Double soma, 304 
Dragonflies, 95 

adult, 233 

Carboniferous, 95 

young, 233 

Ears of grasshoppers, 30 
of katydids, 36 

Egg laying of cicada, 212 

Eggs of aphids, 157, 158 
of cicada, 212 

Culex mosquito, 331 
grasshopper, 5, 6, 7 
house fly, 343 
roaches, 80, 81 
tent caterpillar, 262 

Enzymes, 1 1 1 

Epicauta vittata, 22 

European house cricket, 55 



Fat-body, 260, 292 
Field crickets, 58 
Flies, 314 

horn fly, 348 

horsefly, 320-324 

house fly, 342-347 

in general, 315 

larva, 325 

pupa, 327 

stable fly, 348, 350 

tsetse fly, 348 

young, 231 
Food exchange by termites, 144 
Foot of cricket, 55 

of grasshopper, 32 
katydid, 32 
Fork-tailed bush katydid, 39 

song, 39 
Four-spotted tree cricket, 67 

Gadflies, 320 
Ganglia, 118 
Garden aphids, 171, 172 
Genus, defined, 27 
German roach, 79 

egg case, 8 1 

hatching, 81, 82 
Germ cells, 100, 103, 124, 304 
Glossina, see Tsetse flv 

palpalis, 350 

morsitans, 350 
Grasshopper, 1 

adults, 17 

cousins, 26 

definition, 2 

destruction of eggs by blister 
beetles, 23, 24 

devastation by, 18 

ears, 30 

egg laying, 4, 5 

egg-pod, 5 

eggs, 6, 7 

Grasshopper, growth, 13, 14 

hatching, 8, 9 

head, 12 

males and females, 3 

migration, 18 

molting, 14-16 

ovipositor, 4 

parasite, 19, 20 

songs, 30, 3 1 

spiracles, 13 

wings, 29 

young, 1, 8, 11 
Grasshopper family, 28 
Grasshopper's cousins, 26 
Green apple aphis, 162-168 
Green bugs, 152 
Gryllus, 58, 60 

assimilis, see Black cricket 

domesticus, 55, 60 

Handsome meadow grasshopper, 


song, 54 
Halteres, 319 
Heart, 112 

Hexapoda, see Insecta 
Histoblast, 259 
Histogenesis, 260 
Histolysis, 259 
Honey dew, 155 
Hormones, 119 
Horsefly, 320 

larva, 325 

mouth parts, 321-323 

pupa, 325 

sucking pump, 322 
House centipede, 82, 83 
House fly, 342 

breeding places, 343 

eggs, 343 

larva, 343 

mode of feeding, 346 

mouth parts, 345, 346 



House fly, pupa, 345 

puparium, 344 

unsanitary habits, 347 
Hypermetamorphosis, 250 
Hyperparasite, 181 
Hypopharynx, 108 


Imaginal discs, 259 
Imago, defined, 259 
Insecta, 28 
Intestine, 1 10 


Jumping bush cricket, 69 

song, 70 
June bugs, 230 


Katydid, 43 

habits, 46 

musical instruments, 47, 48 

song, 44, 48, 49 

true, 43 
Katydid family, 32 
Katydids, 32 

angular-winged, 41 

bush, 38 

ears, 36 

musical instruments, 34-36 

round-headed, 37 

song, 1,3, 34 

young, 1 1 
King termite, 134 

Labium, 108 
Labrum, 108 
Lady-beetles, 175, 230 
Ladybird beetles, 175, 230 
Larva, characters, 246 

definition, 245 

nature, 249 

of A'edes, 339 
Anopheles, 340, 34 1 

Larva of Culex, 331, 332, 233 
of flies, 325 

house fly, 343 

mosquitoes, 329 

wasps and bees, 252 
Leaf insect, 71, 72, 73 
Legs of insects, 107 
Lepisma, 93 

Life of a caterpillar, 262 
Locustidae, 32 
Locusts, 2 

seventeen-year, 182 
Luna moth, 228, 230 


Machilis, 93 

Maggots, 252 

Malacosoma americana, see Tent 

Malaria mosquitoes, 340 

adult, 340 

eggs, 340 

larva, 340, 341 

pupa, 341 
Malaria parasite, 342 
Malpighian tubules, 116 
Mandibles, 107 
Mantids, 73 
Mantis, praying, 73-76 

eggs, 75- 7 6 
Maxillae, 108 
May beetles, 230 
Mayfly, 96 

Meadow grasshoppers, 52-54 
Mecostethus gracilis, 3 1 
Metabolism of pupa, 260 
Metamorphosis, 14, 226 

complete, 245 

defined, 227 

diagram, 243 

incomplete, 245 

of tent caterpillar, 297, 299-304 
Microcentrum red nerve, 41, 43 

song, 43 



Microcentrum rhombifolium, 41, 

song, 41,42, 43 

Mole cricket, 58 

song, 58 
Molting of grasshopper, 14, 16 
Mormon cricket, 54 
Mosquitoes, 329 

adult, 330, 335, 338 

Aides, 331 

Anopheles, 331,340 

common, 331 

Culex, 331 

larvae, 329 

malaria, 331,340 

Stegomyia, 338 

yellow fever, 338 

young, 239 
Moth of tent caterpillar, 305 

characters, 306, 307 

egg laying, 312 

emergence from pupa, 305, 306 

mouth parts, 306, 307 

proboscis, 307, 308 

reproductive organs, 3 1 1 
Moths, Cecropia, 228 

celery, 229 

Luna, 228, 230 

Promethea, 228 

tent caterpillar, 305 
Mouth parts, 12, 107 
Musca domestica, see House fly 
Muscidae, 342 

Musical instruments of cicada, 

of crickets, 56, 57 
grasshoppers, 30, 3 1 
insects, 33, 34 
katydids, 34, 35. 3 6 
Myiasis, 352 

Nagana, 349 
Narrow-winged tree cricket, 66, 


Narrow-winged tree cricket, an- 
tennal marks, 66, 67 
song, 67 
Nemobius vittatus, 58 

song, 58, 59 
Neoconocephalus ensiger, 50 
song, 5 1 
retusus, 50 
robustus, 51 
song, 51 
Neocurtilla hexadactvla, 57 
Neoxabia bipunctata, 69 
Nervous system, 117 
Nymph, defined, 245 


Oecanthus angustipennis, see Nar- 
row-winged tree cricket 

latipennis, see Broad-winged 
tree cricket 

nigricornis, see Black-horned 
tree cricket 

nigricornis quadripunctatus , 68 

niveus, see Snowy tree cricket 
Oesophagus, 1 10 
Orchelimum agile, ^3 

laticauda, 54 

vulgare, 52, 53 
Oriental roach, 79, 80 
Origin of insect wings, 91, 92 
Orocharis saltator, 70 
Ovaries, 122 
Ovipositor, 4, 123 
Ox warble, 352 

Paleodictyoptera, 90, 92 
Parasites, defined, 179 

of aphids, 177-179 
grasshopper, 19, 20 
Parthenogenesis, 162 
Periodical cicada, 182 

abdomen, 205 

adults, 199 



Periodical cicada, air chamber, 205 

broods, 215-217 

death of adults, 214 

digging methods, 190, 191 

egg laying, 212-214 

eggs, 212, 219 

food, 200 

front leg of nymph, 190 

hatching of eggs, 217-223 

head of adult, 201 

huts, turrets, 192 

mouth parts, 201-205 

musical instruments, 199, 207- 

nymphal chambers, 187-189 
stages, 186, 187 

nymphs, 185-193, 223-221; 

ovipositor, 199 

races, 215 

salivary pump, 204 

song of large variety, 210, 211 
of small variety, 211, 212 

sucking mechanism, 203 

transformation, 193-199 

two varieties, 199 

young nymphs, 223-225 
Phagocytes, 259, 301 
Phaneroptera, 38 
Pharynx, 1 10 
Phylloxera, 172 
Phylum, 26 

Physiology of tent caterpillar, 283 
Plant lice, 152 
Plasmodium, 342 
Proboscis of moth, 307, 308 
Promethea moth, 228, 229 
Propupa of tent caterpillar, 296- 

Protoplasm, 100 

Pterophylla camellijolia, see Katy- 
Pupa, 250, 253, 254 

added stage in metamorphosis, 
2 54 

Pupa, definition, 245 
of flies, 327 
house fly, 345 
mosquitoes, 334, 339, 341 
tent caterpillar, 298 
reason for, 257 
Puparium, 252 
of house fly, 344 


Queen termite, 134, 149 


Rat-tailed maggot, 327 
Reproduction, 102 
Reproductive organs, 122 
Respiration, 1 14 
Reticulitermes, 136 

life history, 136-141 
Rhadophorinae, 55 
Roaches, 77, 80 

and other ancient insects, 77 

eggs, 80, 81 
Robber flies, 324 
Rocky Mountain locust, 17, 18, 

Rosy apple aphis, 168-170 
Round-headed katydids, 37 

Amblycorypha oblongijolia, 39 

angular-winged, 41 

fork-tailed bush, 39 

Microcentrum, 41, 43 

Phaneroptera, 38 

Scudderia, 38, 39 

Sarcophaga kellvi, 19-21 
Scudderia, 38 
Jurcata, see Fork-tailed bush 
Segments ot body, 12 
Sense organs, 1 21 



Seventeen-year locust, see Periodi- 
cal cicada 
Shield-bearers, 54 
Sleeping sickness, 349 
Slender meadow grasshopper, 54 
Snowy tree cricket, 65 
antennal marks, 66 
musical instruments, 57 
song, 66 
Soldiers of termites, 131 
Soma, 104, 304 
Somatic cells, 104 
Song of insects, 23> 34 
of cicada, 210-212 

crickets, 58, 60, 62-70 
grasshoppers, 30, 31 
katydids, 39, 41, 42, 43, 44, 

47.48, 49> 5 1 . 5J> 54 
Spiracles, 13, 1 14 . 
Spirochetes, 340 
Stagmomantis Carolina, 73 
Stimulus, 106 
Stomach, 109 
Stridulation, 23 
Striped ground cricket, 58-60 

song, 58, 59 
Syrphid flies, 177 

larvae feeding on aphids, 176, 

Sword-bearing conehead, ;o 
song, 51 

Tabanidae, 320 
Tent caterpillar, 262 

behavior on leafless tree, 278, 

cocoon, 282 

egg, 263 

egg mass, 263, 264 

epidermis, 29^ 

fat-body, 292 

feeding habits, 270, 272, 273, 

Tent caterpillar, general external 

form, 285, 286 
head, 284, 285 
internal organs, 289-291 
jaws, 286 

jumping from trees, 280, 281 
manner of feeding, 277 
metamorphosis, 293 
molts, 275 
moth, 305 
newly-hatched, 265 
prepupal stage, 295 
propupa, 296, 297 
pupa, 298 
silk glands, 286 

press, 288 
spinneret, 286 
spinning cocoon, 282, 283 
structure and physiology, 283 
tents, 270 

weaving tent, 272, 273 
young, 262 

in egg, 312, 313 
Termites, 125 

Ame collective, 143 
castes, 131, 141, 142 
community life, 134 
destruction by, 129 
digestion of cellulose, 137 
egg laying, 150, 151 
food exchange, 144 
fungus grown for food, 148 
king, 134 

life history, 136-141 
males and females, 133 
nests aboveground, 148 

in trees, 148 

underground, 147 
queen, 134, 149 
Reticulitermes, 136 
short-winged form, 133, 140 
soldiers, 131 
tropical termites, 146 
winged form, 133 



Termites, wingless males and 
females, 140 

workers, 131 

young, 136 
Testes, 122 
Tettigoniidae, 32 
Thorax, 12 
Thysanura, 247 
Tracheae, 114 
Tree crickets, 63 

antennal marks, 66, 67 

attraction of males for females, 

black-horned, 67 

broad-winged, 65 

four-spotted, 67 

musical organs, 56, 57 

narrow-winged, 67 

Neoxaiia, 69 

Oecanthus, 65-68 

snowy, 65 

song, 65, 66, 67 

two-spotted, 69 
Triungulins, 23 
Tropisms, 121 
True katydid, 43 
Trypanosoma, 349 
Tsetse fly, 348, 349, 350 

mouth parts, 350, 351 
Two-spotted tree cricket, 69 

song, 69 


Walking stick, 72 

Walking stick insects, 71 

Wasps and bees, larvae, 230, 238, 

Ways and means of living, 99 
White ants, 128 
White grubs, 230 
Wings, 83, 8 4 
evolution, 315 
of bees, 319 

beetles, 318 

butterflies and moths, 318 

dragonflies, 316 

flies, 319 

grasshoppers, 318 

roaches, 83, 84, 318 

termites, 146, 316 

wasps, 319 
origin, 91, 92 
Wigglers, 230, 329 
Woolly aphis, 172 

Xiphidium, 54 

Yellow fever, 339 
Yellow fever mosquito, 331, 339, 



3 ^Oflfl 00157623 

nhent QL463.S6X 
Insects, their ways and means of living,